It's not fully arbitrary, but one can make an Apple ID from any email address or phone number (i.e. you can use a hotmail address if you like), both approaches

It's not fully arbitrary, but one can make an Apple ID from any email address or phone number (i.e. you can use a hotmail address if you like), both approaches dodge the issue mentioned since they're not obviously apple accounts. However the issue with using something like a gmail or hotmail account is that instead of targeting Apple's servers, they just target Google and Microsoft's instead.