This is a valid point. FSF is very particular about requiring people to reassign copyrights to FSF when you contribute to GNU software. (It is controversial!) They do this to strenghten their legal stance. They can more effectively defend their license and copyrighted code base if the copyright is fully owned by a single legal entity. I could imagine a legal challenge by FSF backed by legal resources from EFF. All we need to do is get Copilot to spit out some non-trivial code (including comments!) from some core GNU utilities. That should be enough to start a lawsuit.