Cant be just that. You can change your IP, create a whole new browser profile and of course not log into your old account and it will still flag you. It might just be that Im unlucky and for some reason outside of my control whole regions of my ISPs adress space are flagged.
The flag is not on my (usually used) account. I can perfectly use that one (though it seems to be the case that old accounts can and sometimes are flagged, not for me though). It is set on new accounts in an otherwise empty browser profile over a clearnet connection in the adress space of a rather large ISP. So there should be no context to work with at all unless creepy things are done. Having some amount of google cookies didnt help either.