Physbones are an optimized version of Dynamic Bones, the VRChat Constraints are an optimized version of Unity’s Constraints.
Why not create a VRChat Cloth component too?
This has been on the team’s mind since the introduction of Physbones, as it was mentioned in that same video (why was it deleted by the way? absolute peak VRChat days). The cloth component has been known to be very frame hungry, and many would love the new world of expression this would offer!