> along with the optional “one mailbox, infinite aliases” feature we’re discussing right now.

They’re not exactly the same thing. Aliases are alternate addresses (under one domain) you set up yourself, while a catch-all just accepts any address in the domain as valid. While iCloud Mail does allow catch-all¹, aliases are capped at a maximum of three².

¹ https://support.apple.com/en-gb/guide/icloud/mm9e3ee0680f/ic...

² https://support.apple.com/en-gb/guide/icloud/mm074af79454/ic...