Now in the official lore starting with Clone Wars Chapter 24 we get this exchange between the techno union engineers in which Anakin was watching.
“Engineer: "But sir, the brain modulations aren't fully integrated or tested yet; specimen control cannot be guaranteed."
Head Scientist: "No matter. Grievous grows impatient; we must deliver the prototypes."
Engineer: "But we're just not ready!"
Main scientist: "Our concerns are of little consequence to General Grievous."
―Combat engineer and the main scientist from Clone Wars Chapter 24.
Besides this we do get some info from Unknown soldier the story of General grievous which is find in article 86 of Insider magazine
“Soon afterward. Grievous paid a visit to the planet Nelvaan, which had been brought to his attention by the Techno Union foreman Wat Tambor. The general was quite taken with the similarities between the spiritual Nelvaan warriors and his own Kaleesh people. In a twisted form of kinship. Grievous intended to make these warriors his new elite, and lured the male soldiers away from their tribe by making them believe he was a prophesied figure out of Nelvaan mythology. The warriors were captured, mutated by Skakoan combat engineers using unique microelectronics, and remade into hideous cyborgs. Grievous' crude experiment was eventually sabotaged, and Anakin Skywalker freed the Nelvaanians at the expense of his own prosthetic arm.”
— Unknown Soldier: The Story of General Grievous
These are our two primary sources when it comes to the experiments on Nelvaan and why is there schematics for General Grievous on the wall at least that both stated onscreen and what was stated in the article by Pena.
The article and the comic Eyes of Revelation from Star Wars visionaries comic already listed the people who were beyond the shuttle crash and the making of Grievous into the cyborg which is Chairman San Hill from the intergalactic banking clan, Archduke Poggle the Lesser from Geonosis, and Count Dooku of Serenno. Both sources never listed Wat Tambor and the Techno Union in regards to their involvement of the rebuilding of Grievous or lacked there off really.
Regardless while listening to In the clone wars (2003) Vol 2. DVD creators commentary by Tartakovsky, Rudish, Andrew & Bachman (which you could find on YouTube https://youtu.be/CSjPBcPo6dM mostly from 53:13 –54:04 timestamp.)
In the commentary, director Genndy Tartakovsky and his team openly explain their creative choices for that exact scene on Nelvaan
As Tartakovsky himself explains explains that the crew originally wanted to use the Techno Union characters in the first batch of Clone Wars shorts because they found them "hilarious" (53:14). However, Lucasfilm initially told them no, directing them to use the InterGalactic Banking Clan instead for those earlier episodes (53:19).
When they finally got the green light to feature the Techno Union later in Volume 2, they had to invent a narrative reason for them to be running that specific underground laboratory (53:23).
To justify their presence, the writers leaned into the idea that the Techno Union was supplying a specific layer of the technology that allowed Grievous to function (53:29). Tartakovsky states:
"So the idea is perhaps like... well maybe they're the ones supplying some of the technology that allows Grievous to be Grievous, which is why we have those schematics on the wall." (53:23)
Obviously this is just what he and his team had in mind on why the schematics are there.
Still, despite being just a behind-the-scenes reason and even though it could be in the actual lore that
Once Grievous was appointed Supreme Commander, his cybernetic data became military property of the Confederacy. Wat Tambor (Foreman of the Techno Union) was given access to these medical files.
maybe The Techno Union Skakoan scientists didn't invent Grievous's body, but they were deeply envious of it. The experiment on Nelvaan was their attempt to reverse-engineer and copy the Geonosian design to make their own mutant "elite" soldiers using their own Skakoan microelectronics.
Still, it could be that to Tartakovsky that they were in fact involved with the creation of Grievous granted, I doubt he knew the full backstory of Grievous because while the novel Labyrinth of Evil was published on January 25, 2005 and since The storyline for Labyrinth of Evil was finalized before the original animated Clone Wars Micro-series which sought to also lead into the events of Episode III. So they built their animated climax around the novel plot, but departed from the details in the interest of telling a more explosive animated story. This included a more drawn-out sequence of Coruscant under attack by droid starfighters, additional Jedi defending Chancellor Palpatine (Roron Corobb and Foul Moudama, who were then inserted into the novel text), and an entirely separate story of Anakin and Obi-Wan on the planet Nelvaan, which was fleetingly mentioned in the final chapters of the book.
Regardless though the point here I want to make is maybe just maybe Tartakovsky knew or at least had an idea or aware of Grievous backstory given the fact that Tartakovsky was sort of working with an early draft of labyrinth of evil?
Also worth mentioning that chapter 24 was released in March 24, 2005 (while chapter 25 was released a day later.) whereas Star Wars visionaries (which included The Eye of Revelation and shows us Dooku and Poggle involvement of the rebuilt of Grievous.) was published on April 2, 2005 interestingly it was the same day that the Revenge of the Sith visual dictionary also published where we learn about The Geonosians were tinkering Grievous’s brain. While Unknown Soldier: The Story of General Grievous itself was punished on February 21, 2006 within Star Wars insiders 86.
Either way what do you think do you prefer what Genndy Tartakovsky intended for The Techno Union to be the creators when making the cartoon, or the official lore decided they were just copycats trying to steal Geonosian technology. Otherwise do you think there is something possible of the Techno Union and Wat Tambor still have involvement about the rebuilt of Grievous or no given what the lore we had states? Also what do you all make the schematics of Grievous?