Okay, I see what you mean. We never paid attention to whether (1) was happening. I imagine Apple can tell based on the code that was running at the time.
Even in case (1), isn't it possible that Hide My Email bounces happen differently from regular @icloud.com bounces despite being on the same domain?
We've also been wondering whether Hide My Email was ever responsible for generating the messages with meant-to-be-hidden addresses or whether it was only passing them along and failing to hide them. I don't think we have enough information to tell.
Even in case (1), isn't it possible that Hide My Email bounces happen differently from regular @icloud.com bounces despite being on the same domain?
We've also been wondering whether Hide My Email was ever responsible for generating the messages with meant-to-be-hidden addresses or whether it was only passing them along and failing to hide them. I don't think we have enough information to tell.