It it is still pretty unlikely, and when you think about it, the only thing that might be discovered is your email which is not all that private anyway. Apple, and Microsoft also have distribution platforms you don’t want to be locked out of.
E2EE doesn’t really have any real bearing here as it’s not a chat platform we’re talking about.
Yeah they’re not going to tell Amazon to suddenly not ban my account unfortunately. This is why I don’t recommend using those domains for things you truly care about eg any kind of distribution platform where you’ve paid for licensed content (eg Steam, Epic, etc).
Aliasing services are good, but knowing where to use them is important. I would highly recommend reading the Complicated is Better misconception that I wrote back in 2022.
As it seems you’re pretty set on Proton, (they’re a good provider and very good for people who don’t know much technically). The reason I say this is they have quite good documentation, and in one particular consulting job I did (small business) we used that @family.com domain.
They use SL for various accounts they don’t care too much about and have an additional custom domain @some_word_they_all_liked for still “known identity” stuff that they wanted to keep separate from @family.com