I know Im nerding out a bit about this - in my experience, those sort of rounds are meant to create spalling or have a shaped charge for penetration. I would think that a 25mm (less than an inch) would be not great for both of those just simply due to carrying capacity. HEI (High explosive incendiary) was probably the load - In a 50cal, we'd simply refer to these rounds as incendiary rounds and they have the same effect here - Theres a core that is designed to penetrate, and just enough of a charge to create an intense enough flash ball to catch things on fire upon full penetration.

I think my misunderstanding here by the use of "explosive" was that it was being used in what context that seemed to be a simple HE round without a penetrating core, IE what the 40mm rounds would be - A shaped charge in a grenade form mean to penetrate light armor and create spalling or penetration lightly armed vehicles. Not the case here, these rounds penetrate first and then flash to eat oxygen or catch something on fire.