A person's testimony is a source. I can add mine: you can tell when you're truly blocked because if you click for the accessibility audio-based captcha it will actually tell you you're blocked (but, if you did the visual captcha, would simply loop forever while telling you you did it wrong).

I don't think you'll find an article by Google saying "yes, we sometimes completely block users while making it look like they're not blocked and wasting their time".

Depending on the IP reputation as well as the kind of IP address you have, this can happen.

Google also prefers if you have a Google account logged in.