Why shouldn't collision meshes overlap?

I’ve just started learning Unreal Engine (I’m still pretty new to 3D game development in general), and was trying to figure out how to utilize a mesh designed in Blender as a level. I came across this page which seemed to answer my question about how to make collision geometry in a modeling tool. The page says that “In the case of an object whose collision is defined by multiple convex hulls, results are best when the hulls do not intersect with one another.” Why is this? If I am making collision geometry in Blender, is it true that adjacent collision meshes must not share any vertices (or overlap)? I would have thought it would be bad to have gaps between collision meshes. What are the consequences of overlapping collision meshes? If a gap is necessary, how much of a gap is recommended?

Thanks in advance!

When you go overlapping collisions it tends to cause Unreal to get confused with its built in calculations, Because of this you can butt the collisions up against each other just can’t over lap. As for a gap, think of the size of the players you are using and if they can fit through the gap then it is to big. When I make my collisions within 3ds max I tend to make them just a hair smaller than the object I am using them on. It creates clipping issues are times but sometimes you can’t get away from it.

I hope this helps