I hadn't! I just gave it a shot and it seems sadly it suffers from the same problem. If I try and reply to an email received via SimpleLogin, it leaks my real email address (no option to reply as the receiving address), protonmail-bridge rejects it as a sender as well same as a catch all reply. Unfortunate.

Edit: Seems there is a reverse alias option, and seems to work well, will give it an honest go before migrating, thanks for the tip.