That’s typically not a disguise but a clear means of indicating that you can reply to the email
That is not how spam filters work.
Gmail added a popup asking the user if they want to unsubscribe when flagging a newsletter with the appropriate unsubscribe headers, so it must be common enough to warrant Gmail developer attention.
Unfortunately close to 100% of the spam I'm flagging causes this popup now :-/
I'm getting a dozen spam a day now on my Gmail account ... I think they're losing the battle.
Sounds like it's gotten even worse.
In which case, people like me with an @hotmail.com address from the 90’s were much earlier users of the outlook.com email boxes than when the domain was “launched” by Microsoft.