Earlier quoted context omitted.
The bounce rate of what, exactly? Because the bounce rate of Hide My Email addresses being deliverable is going to rise over time, by design. Whenever I start getting spam at an address that's been leaked, I deactivate it. I've done the same with my oldest gmail account, but the work required there is notably higher.
If they were moved to plain old icloud.com, I could absolutely see a bunch of companies starting to filter out all icloud.com email addresses to avoid private relay. Either just because they’re jerks or from bounce issues. Keeping it on a subdomain fixes that problem, to some degree. If the user is named ffjvhtu57325cjdjvg501a2@icloud.com no one is going to think that’s a real address. It’s very obviously a private o…
They are not changing the subdomain. There isn’t one. The announcement is they are leaving it as-is.
The email addresses for sign-in with Apple do use the @private.iCloud.com subdomain, but again, that’s not a change.