Email routing - reject (instead of drop) specific address

In my existing mail setup, I use catchall addresses for some domains. If I start to get spam at a specific address, I can reject (with a 550 SMTP error code) mail to that particular address, while still receiving mail to all other addresses via the catchall.

Playing with CF Email routing, it seems that if I do not have a catchall, then any mail to a non-existent address will get a 550 SMTP error, which is a good thing. But if I provide a catchall, then it seems like I can no longer block a specific address and return an error. I see that there is a “Drop” option, which allows mail to a specific address to be silently dropped. It would be nice if there was also a “Reject” option, to refuse the mail at the MX interface and provide an error to the sender. I realize that in most cases, spammers don’t care about errors, but in the (hopefully unlikely) event that a legitimate sender for some reason sends email to an address I have blocked, I would like him to receive some notification that the mail will not be delivered