Additional information about the "popgroups" file

We know that in this list below there are the locations where the cars in each area circulate, but where the “net_common” and “net_uncommon” vehicles are located, I recently realized that on my server there was a MOD car inserted within “net_uncommon”, but I never I saw it on the street, not even parked. Where could he be? Another question too, which one between “veh_mid_mp” and “veh_mid”?

These are assigned to areas via ‘zonebind’, though I believe in FiveM the SP assignments are used, and not the MP assignments.