Oh ya, I get that. But the goal is to avoid reusing an address that's used in a different tx, on the output side of the coinjoin. If you can guarantee that never happens, even if the recipient of some UTXO's in the coinjoin is distinct from the sender who owns some inputs in the coinjoin (for example I'm making a donation to some org via a coinjoin), without requiring interaction from the recipient, that would be good and worth added complexity to do the silent protocol within the coinjoin.