Yes, to fully fix a certain class of bug on their infra.

A lot of places also don't really like icloud addresses in general. This is one of Apple's better offerings though.

Anyone have a theory why this even made it to this point? the switch was such obviously a bad idea. just corporate weirdness that no one there bothered to raise their hand and be like "uh, are we really doing this?" or was there a story here that anyone knows about?

It's talking about two different services:

> Sign in with Apple addresses, previously issued on privaterelay.appleid.com, will be issued on private.icloud.com.

> iCloud+ Hide My Email addresses will remain on icloud.com.

Sign in with Apple is Apple's SSO, like Sign in with Google. Services have to support this one explicitly, and it already had a special subdomain, so the specific subdomain is simply changing.

Hide My Email is the manually generated ones, for websites that accept an arbitrary email address. This is the one where it's valuable for the relays to be identical to genuine iCloud addresses, otherwise websites could try to block it and force you to use a more revealing email address, undermining privacy.