If a spam service erroneously marks one email as spam, chances are it will also marks other very similar emails as spam. So it's not too surprising all three were marked.
For these kind of automated emails getting all emails consistently being delivered to everyone is really hard, almost impossible.
The problem here isn't really that emails weren't being delivered, it's that they seem to have tried only one method to contact people, didn't check how successful that was (e.g. by seeing how many customers were still on those regions), and seemingly never tried anything else (such as notifications on the dashboard, a temporary brown-out to alert people, etc.) – "we tried one way to contact you and that didn't work, so we just deleted your service sucks to be you lol kthxfuckitybye"
For these kind of automated emails getting all emails consistently being delivered to everyone is really hard, almost impossible.
The problem here isn't really that emails weren't being delivered, it's that they seem to have tried only one method to contact people, didn't check how successful that was (e.g. by seeing how many customers were still on those regions), and seemingly never tried anything else (such as notifications on the dashboard, a temporary brown-out to alert people, etc.) – "we tried one way to contact you and that didn't work, so we just deleted your service sucks to be you lol kthxfuckitybye"