> FB probably owns copyright on some of the data used for instruction tuning the model,

I'm not so sure they do, and even if they did so what? Holding the copyright on some of the data being used in the model doesn't mean they hold the copyright on the model.

> They want to have their cake and eat it

Nemo auditur propriam turpitudinem allegans.

That's what my comment tried to say but flubbed it a little bit