If you didn't want to be credited you should have said.
Signed-off-by probably has some legal weight. When you add that to code you are making a clear statement about the origins of the code and that you have legal authority to contribute it - for example, that you asked your company for permission if needed. As far as I know none of this has been tested in court, but it seems reasonable to assume it might be one day.
Newcomers see everyone saying balacalaboozy, so they say it to. It doesn't mean that they have read or agree to the doc that declared its meaning.
LLMs are the world's most sophisticated copycats. Surely they too will parrot balacalaboozy, unless their training is updated to include, understand, and consistently follow these new guidelines.
I don't see how the "signed-off-by" attestation constitutes correct credit here. It's claiming that GP saw the final result and approved of it, which is apparently false.
Hypothetically in court you'd go to the last, ask "did you write this" and only if not go up.