On PhysBones you can set if it should collide with your own colliders, the colliders from others or both.

The newly added global colliders don't respect that however. They will collide with PhysBones that have "Allow Self" disabled.

A manually added global PhysBone collider should be treated similarly to your default colliders. Disabling "Allow Self" on a PhysBone should also disable a local global PhysBone collider from colliding with it.

Here you can see the global collider still colliding with my toes even though I have "Allow Self" disabled. (The last screenshot is in Play Mode)