Why is the option to send verification code via text not available on iCloud for Windows?

There's an issue with Advanced Data Protection for Windows 11.

When enabled on your Apple device and then signing into iCloud for Windows, you're sent a verification code. This code immediately disappears. This is a bug that's been around for years, but not the main issue. What is though is the option to send a verification code via text is not available. That means you're unable to login.

You can generate a verification code from your Mac. That does not work though. Also recent updates to iCloud for Windows have no effect; I'm running 15.0.215.0. Reinstalling iCloud has no effect either.

You can turn off ADP, login successfully (the option to send a verification code via text suddenly becomes available again), then turn ADP back on and use iCloud for Windows. However, the iCloud Drive section will stop syncing after a while. It will either get stuck uploading files, or stuck initialising.

Via screen sharing I demo'd all this with Apple tech support.

[Re-Titled by Moderator]