I have no problem with thank you notes; I think they’re courteous and easy to send. It never hurts. If you don’t get hired you lose nothing, and if you do, you’re starting on a pleasant note.
But I would definitely want to know more about the governance of an organization that can sustain such a policy as categorically rejecting a candidate (read: contribution) for not meeting an unexpressed expectation.
As a UK interviewer I'd find them both unusual and annoying.
We already discussed you immediately after the interview. It's not going to change anything, but it might hurt your chances if it comes across as cringy or brown-nosing - we're also looking for cultural fit, and most Brits just don't do that. If you introduced new information in the email, you're probably going to force us to discuss you again, which is at best annoying and certainly burns up staff time.
So in a UK context, you're best off just saying "Great to meet you all - hope I'll get to work with you" at the end of the interview, and leave it at that.
But I would definitely want to know more about the governance of an organization that can sustain such a policy as categorically rejecting a candidate (read: contribution) for not meeting an unexpressed expectation.