1. For the record: the GPL is entirely dependent on copyright.
2. If AI "clean-room" re-implementations are allow to bypass copyright/licenses, the GPL won't protect you.
This is right up there with Meta lawyers claiming that when they torrent it's totally legal but when a single person torrents it's copyright infringement.
Isn't that the same for the obligations under BSD/MIT/Apache? The problem they're trying to address is a different one from the problem of AI copyright washing. It's fair to avoid introducing additional problems while debunking another point.
2. BigCo bus Company A
3a. usually here BigCo should continue to develop Project One as GPLv3, or stop working on it and the community would fork and it and continue working on it as GPLv3
3b. BigCo does a "clean-room" reimplementation of Project One and releases it under proprietary licence. Community can still fork the older version and work on it, but BigCo can continue to develop and sell their "original" version.
patents protect ideas, copyright protects artistic expressions of ideas