yea that vampire survivor-esque push out solid thing you made is nice!
I guess the build in collision cells must update when an instance moves I assume (well not the whole thing but the specific instance) instead of just every frame. Plus they also handle objects with different sizes.
I'll check the spacial hash out you linked, definitely seems like a custom solution is the best for extreme cases.
Still would be awesome to have access to the build in system and I assume (naively) it shouldn't be much more work for Scirra then to expose the interface.