A human being who has learned from reading GPL'd code can make the informed, intelligent decision to not copy that code.
My understanding of the open problem here is whether the ML model is intelligently recommending entire fragments that are explicitly licensed under the GPL. That would be a licensing violation, if a human did it.
Actually, I believe it's tricky to say if even human can actually do that safely. There's the whole concept of "cleanroom rewrite" - meaning, if you want to rewrite some GPL or closed-source project into a different license, you should make sure you never ever seen even a glimpse of the original code. If you look on GPL or closed-source code (or, actually, code governed by any other license), it's hard to prove you didn't accidentally/subconsciously remember parts of this code, and copy them into your "rewrite" project even if "you made a decision to not copy". The border between "inspired by" and "blatant copyright infringement" is blurry and messy. If that was already so tricky and troublesome legal-wise before, my first instinct is that with the Copilot it could be even more legally murky territory. IANAL, yet I'd feel better if they made some [legally binding] promises that their model is based only on code carefully verified to have one of an explicit (and published) whitelist of permissive licenses. (Even this could be tricky, with MIT etc. actually requiring some mention in your advertising materials [which is often forgotten], but now that's a completely different level of trouble than not knowing if I'm infringing GPL or some closed-source code, or other weird license.)
My understanding of the open problem here is whether the ML model is intelligently recommending entire fragments that are explicitly licensed under the GPL. That would be a licensing violation, if a human did it.