My first thought is; on a standard snow chain, when the wheels spin (skid) the chain fixed to the wheel gives you grip by being fixed to the wheel. Does that make sense?
These will just be pushed out of the way by the action of the tyre slipping on the road surface. Yes another short length is immediately launched under the tyre but only to be pushed out again.
I'm sure it improves grip but not by much. I prefer the James May funnel and gravel approach. You can smash more windscreens with gravel than just the occasional decapitation.