Sorry, we don't know the reason why Apple has come to that conclusion. There have been no other posts here where the Apple ID had to be abandoned on the Apple TV+ service. As stated, being locked out for incorrect password attempts is a common occurrence for those that have forgotten their password, but the reset process normally goes on without a hitch. I can think of one scenario where it would be required to change your Apple ID to a new email address, but changing your Apple ID also transfers your subscriptions and it can only be done after it has been unlocked.
The scenario would be if a person went to a location and logged into Apple TV+ on someone else's TV, such as an AirBNB and did not log out. There would be repeated requests to access your account and you would be forced to change your password. I could see repeated password guesses by another person at that location and it would continually lock your account requiring the Apple ID email change.
If someone does know your Apple ID and Password, then they can take over your account and it will now be theirs. The password reset process relies on information you have on your account, such as Trusted Phone number and personal information, all of which can be changed if someone already has access to your account.
I do agree you should get refunded $4.50 for the half of the subscription you were unable to use.I also wish we knew the details for why your Apple ID had to be abandoned, but we don't know those details. I totally agree with everything you said in your top post, the second post was uncalled for and post that was removed obviously violated the terms of use for this site. You will find people are much more willing to work with you when you are not saying, if you don't give me my $4.50, I'm going to plaster over Social Media. That never seems to work no matter how frustrated you are.