Question Animation Rigging: Rig with weight of 0 still affects model significantly

I'm finding some weird behavior when I've set the Weight of a constraint to 0. In this case, I have a Humanoid model, with a simple walking animation. I've set up an IK constraint for the left hand, which I thought I could temporarily disable by setting the weight to 0. But instead, the left hand just kind of stays off to the side.

The normal walking animation has both arms swinging at the sides:



But with my Left-hand IK rig enabled, but with its weight set to 0, the left hand just hangs out away from the body:



If I disable the Rig Builder component, then the animation goes back to normal. But with either the Rig's weight set to 0, or the Constraint's weight set to 0, I get the weird behavior.

Here's the constraint I'm using.



I've also tried adding another "empty" rig, with no constraints, with a weight of 1, thinking maybe it's not okay to have no rigs. But that doesn't change the behavior.

Anyone know what's going on here, where a weight of 0 is still affecting the position of the hand?

 

An approach I took to fix a different animation rigging issue seems to have resolved this as well. I've described the approach in the other post:

https://forum.unity.com/threads/ani...ected-by-motion-of-model.926585/#post-6061991