I kinda agree… and I’ve been caught by this recently.
But, to offer another perspective: auto-channel means “take the incoming data on this one channel and forward it to another channel”. When the gear is set up to use auto-channel, the actual destination channel is unknown. you may know that the destination is the right one, but the “essence” of using the auto-channel is that it could end up anywhere.
Sync makes more sense to have an explicit end point (a channel destination), because it wont ever change (through any given performance). So “leaving it to the auto-channel to figure out” doesn’t actually make sense.
Now, I know this is totally waffly, because ultimately the same channels should get used. It’s just a story, and perhaps a design guide.