Indeed - but replying from an arbitrary address is one big downside of G Suite’s implementation. In FastMail you can add <star>[0]@example.com as an identity. Selecting this when composing an email allows you to edit the localpart entirely. Similarly, when replying to an email sent to your catch-all and you have an <star>@ identity for the hostname FastMail will automatically set your from address for you.

In Gmail (with G Suite) one has to manually add every identity they may wish to reply from - there’s no <star>@ option. Additionally, it’s impossible to hide your real email address/Google Account address. It’ll always be disclosed in the email headers unlike FastMail.

I’d love if G Suite would make such a workflow easier..

[0] escape characters don’t seem to work here, <star> refers to what’d you think it does