Which enemies are you talking about? The mod doesn't outright multiply mobs, it selects more mobs from the spawn pool. Some of the enemies have yellow name text when they shouldn't have, which means they're designated as Champion mobs. Champions only get 2x more spawns (or 3x on XMAX mode.) It also depends on whether the mob pool has enough mobs in it, if there aren't more mobs in the pool then it can't spawn any more. There are generally a lot of bugs and lower quality assets in the expansions, so I wouldn't be surprised if some of the pools are lacking mob variants.

like the crabs at the start of Act 4. or the mosquito/lion enemies right outside Gadir in atlantis don't get multiplied at all.
playing on xmax+ (10x + 5x bosses)

The antlion enemies only have 3 mobs in their pools, and the default setting is that it'll spawn 2-4 of them, even though 4 isn't even possible. So the mod just guarantees that the maximum of 3 will spawn. Normally, multiple pools are designated for each spawn point, allowing this mod to work, but the developers threw out that "multiple pools system" for these enemies. Not much I can do.

The crabs in act 4 is almost the same story. The files that designate the multiple spawn pools only has a single pool in them, and that pool only contains 2 normal mobs, 2 champions and 2 heroes. Only the normal mobs are really relevant. If I were to fix bugs like this then I'd have to expand all the pools for normal mobs instead of just boss pools. Not very likely that I'll ever do that, it's asking too much of one guy and his spare time.

Btw, this is why it's called xMax instead of x10. It reaches the maximum amount of spawns in most of the pools.

fair enough, thanks for the details at least.