Wild encounter rate filters in Gen II wasn't actually a problem in most cases since you could always force an encounter with Sweet Scent (unless you're looking for the Roamers), or have the rate doubled by playing Pokémon March. However, encounter slots may place a stricter limitation than Gen I as all random values larger than 100 will be discarded.Something that's been nagging at me: Does Gen II's random number generator behave similarly at all?
Even if we take both encounter rate and slots into consideration, there are still possibilities for the game to make extra random calls before DV generations. For example, Gen II will make a random call to determine if there's an item on a wild Pokémon before generating its DVs, and if yes, an extra random call will be made to determine if it's a common or a rare item. Extra random calls like this could result in a different spread.
By the way, can we assume that "hRandomAdd and hRandomSub can be in any combination (i.e. hRandomSub could be any value regardless of hRandomAdd)" after a Random call? Since Gen I uses hRandomAdd to determine encounter and hRandomSub to determine the slot, shouldn't the DV spread be limited only by encounter rate and not the encounter slots if that assumption holds?