Email Alias Permanently Linked to Apple Account - Apple Won't Remove it... Why?

Don't confuse an alias with the primary user name for an iCloud mail account. You can only have one primary username which is the permanent identifier for a mail account. It cannot be changed. Aliases can be changed as outlined in Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

Nobody on this forum works for Apple. We only know what's in their documentation, or our own experience or what others say (which we have to take with a grain of salt). Apple almost never provides its reasons for its decisions and they don't like us making speculations about their reasons.

I am not clear what you mean when you say alias. I only know if it in one context and you yourself can alter it. Read about that in Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

If you mean something else you will need to be more descriptive since that is the only time I know of Apple using the word "alias".

I have no idea to what you are referring. If there are other threads then perhaps you could direct me to them. I have to wash windows at home today and I have to have lunch so I don't have a lot of time hunting for threads using terms such as "(?)". I am not remembering ever seeing any thread like that in the 20 years I have been on this forum.