Nerd question: what are the in-wear physics of this item? It looks like a mass on a spring: the phone is a relatively heavy weight, and the wool pocket and str

Nerd question: what are the in-wear physics of this item? It looks like a mass on a spring: the phone is a relatively heavy weight, and the wool pocket and strap are naturally springy. So during everyday wear, does this thing bounce around? It seems like it would be impractical.