Deleting iCloud.com aliases when primary email is Gmail

On iCloud.com My acct has a primary email which is Gmail. I also have 2 aliases listed under it (the@icloud.com & the @me.com) I’d like to delete both aliases permanently. However, even though it’s listed correctly when I try to simply delete my @iCloud alias

It doesn’t allow it & has even said it IS my primary email & seems to disregard my Gmail.

[Re-Titled by Moderator]

Original Title: Delete aliases