I had to check myself, and there are serial/IMEI numbers there, at least the last-five version of each... maybe they store partial hashes instead of the full numbers (hopefully, but I'm a pessimist)
You enrolled in an optional program for personal use. It’s different if Apple coopts that for a different use and the set is likely incomplete.
iCloud ≠ email. I have an iCloud account with a non-functioning e-mail address.
Did you set it up a long time ago? It appears new iCloud accounts require a phone number for 2FA.
LOL, you're one step away from writing a cautionary Medium post.
I believe you can set up an iCloud account with just a phone number.
The fact that you can see them does not mean that Apple can. Wouldn’t be surprised at all if they couldn’t.
The Apple Store (online/iOS app) suggests accessories/confirms accessories are compatible with your devices when shopping, so they have some info.