I dont know if there is an in-engine limitation, or if the effect is not desiderable because things are working as intended, but:
Make tiny mob traversable, akin to how incorporeal mobs can cross people to get past them.
it makes little sense that people gets bodyblocked by one inch tall spiderlings. Even a gnome could leap across a spiderling. Same goes for small oozes, squirrels, and also birds and the likes (just duck, the action not the animal).