It's obvious that IVAS has grown organically out of ENVG-B sharing the philosophy "Designed by Soldiers for Soldiers", same team developing with the same personnel. Additionally the "Need for Speed" in Fielding dictates no need for change if the original ENVG-B/RTA/FWS worked as designed and it does.

"Soldier touch points help us better demonstrate technology, like the IVAS, at specific points in the development process, the cross-functional team gets direct feedback -- and if something fails -- it fails early and we learn from it," said Gen. John M. Murray, commanding general of Army Futures Command.

The current IVAS touch point was led by AFC's Fort Benning, Georgia-based Soldier Lethality CFT in conjunction with the command's Orlando, Florida-based Synthetic Training Environment CFT. They were joined by industry partners to gather tens of thousands of data points and direct feedback to spur rapid iterations of the IVAS design and technology before the next touch point takes place in the future.

Regnier said he has been with the IVAS project since its inception and has also provided technical advice on the development of another device recently fielded, the Enhanced Night Vision Goggle -- Binocular, or ENVG-B, which the Soldier Lethality CFT coordinated.

https://www.army.mil/article/230214/soldier_feedback_driving_army_modernization