Really? I thought that was the standard type of shell. Do the typical unitary shells detonate on impact with the ground, then?

at least judging by most of combat footage i've seen, this is the most common case. consider however that "artillery" is a mix of everything between 60mm mortar and 155mm howitzer, and only some of these have airburst as a standard option. also consider that despite flashy public announcements everyone clears their magazines out of old kit, and this means mostly older type, PD fuzed ammunition. Albania for example sent chinese 81mm mortars, which means it could be from 70s or so, and it's hardly an exception

cluster bomblets for drones make sense, because cluster bomblets are already designed to be dropped at relatively low speed, have fins or ribbon so that they hit target the right way, have appropriate size and weight, are DPICM so are both antitank and generate fragments, it just makes sense

grenades are probably one of the least resource intensive weapons to develop in this situation btw, and really, about everything that drone can lift was already used as drone dropped ammunition. hand grenades of all manufacturers including thermobaric, 30mm VOG-17, 40mm projected grenades, both western and eastern, RPG warheads, 60mm mortars, 81/82mm mortars, DPICM elements, at least few instances of 120mm mortar, and many, many custom made devices including 500ml fanta bottles