If I understand correctly, plug-on neutral panelboards allow GFI/AFI breakers to be installed without running a separate neutral wire (pigtails) from the breaker to the neutral bus bar, and they have the neutral wire from a branch circuit's load cable also attached to either the breaker or part of the panelboard in the immediate vicinity of that same breaker for the branch circuit, which also means non GFI/AFI breakers do not need a neutral wire routed to a dedicated neutral bar either, but the ground wire from the cable would still need to be routed to the neutral bus on a main service panel, or the ground bus on a sub-panel on all of the plug-on neutral panelboards I have seen regardless of the type of breaker or whether or not it is plug-on neutral.
Why do the manufacturers of these panelboards not do the same thing with the ground connection? Couldn't the breaker or its slot on the panelboard simply accommodate a third screw that could send the ground connection to a common bus without needing to route wiring to a dedicated bus bar location that is remote to the breaker in the box? Even in a subpanel, where the ground and neutrals need to be on separate buses, why not have things "under the hood" take care of the proper bus routing for neutral and ground? It would seem like it would be way more neat and less work to install.
I have not seen every panelboard that has ever been made, so I suppose it could exist and I just don't know.