It's strange for SMS/MMS, where recipients are explicitly listed.
I don't think there's a practical use preventing the arrival of such messages, but on a technical level it's a bit peculiar.
I'm not familiar enough with the RCS spec to know if RCS has the same design or if it's simply incapable of hiding messages from members of a group chat. In encrypted chats, you'd expect encrypted messages to become undecryptable for blocked recipients at least, that's one of the major advantages of using encryption, but I guess there must've been a reason why this wasn't implemented.
I have a friend who is too beautiful (and unfortunately meek) for her own good, attracting stalker types with horrifying regularity. This is a great change.