Which is exactly why there's a need for thermobaric warhead option, one shot and the strongpoint with be the defenders' burial mound.I dont think that they would want to sacrifice the flat trajectory in favor for more explosive material. Or else, they can just go with the underslug design that is being thrown around here and cited even in Chinese forums by people who are vehemently against the OICW concept.
What they probably fail to realize is that a higher speed grenade with lower drag and flatter trajectory is a lot more accurate and hence more capable of inflicting critical damage even with lower explosive load. Even with a killing radius of just a single meter, an accurately placed airburst grenade into the firing ports of a defensive position will kill or seriously wound the enemy who is shooting out of it. As long as your explosive charge isnt that of a tank gun or a 1000lbs bomb, accuracy trumps explosive power.
Also, a smaller and faster grenade might also be able to rip through anti-grenade nets set up by the defender to prevent slower thrown or launched grenades to get through firing ports or windows. Airburst function might also be applied here to good effect to counter such defenses.
refer to this info graphic: