Could someone elaborate on what the CompositeCollider2D.GeometryType documentation means by "unwanted collisions?"

I'm trying to understand the pitfalls of using CompositeCollider2D with GeometryType set to Polygons. The unity documentation for the property states that

This is usually the least efficient geometry to use as it produces multiple shapes or edges. These multiple shapes cause unwanted collisions which is where two separate Colliders get in contact even though both are aligned perfectly.

I don't fully get what they mean here. Are they saying that the multiple convex polygons generated by the CompsiteCollider2D will generate contacts every frame even though they are perfectly aligned? Is that true even if the associated RigidBody2D is marked static? If that is the case then why wouldn't these polygons be automatically be masked in a way the turns off collisions between them? They should be placed in a layer or something where there are no collisions between objects of the layer.