Correct. RS-485 is not as easy, because it doesn't have a dominant bit state.

This makes it harder to recover since a collision will almost certainly destroy both transmissions. Also, without a dominant bit state it isn't as easy to guarantee that two transmitters at each side of a very long cable will always be able to destroy the local reception for each other. The cable resistance may not represent enough load to give a destroyed bit at all points in the cable.

But the loopback function do help, and I think it should be used if the extra output pin can be spared (or alternatively if it is ok to hard-wire the receive enable signal).

Everytime you do manage to see a collision, you save a lot of time on the arbitration recovery compared to if you have to wait for a nack or a missing ack. And a missing ack may just as well represent a missing or broken node.

Nicest is when many symmetrical notes can auto-detect each other.