It seems very dependant on brand, model, etc also. Remember these were deisgned to be point to point communications so each maker tweaks the design a bit so they work best within their own brands. Comms like HAM or CB were designed to broadcast to anyone listening so they tend to be more standardized.
I was showing my handheld CB to someone and they kept asking where the other one was and couldn't get it that there doesn't need to be another one paired with it as it was designed to talk to anyone not another single one.