I'm not sure how "ping" can go after knocking, maybe what you have felt is not what you think. When a bat is pressed it still needs further hardening and if you pressed it harder the compressed area would be too thick to allow rebound, so we strike it and this develops a thin hardened layer which allows the spring from the unpressed willow beneath, when the bat has been used a lot the top hardened layer will thicken until the spring starts to fade, I do very much doubt that you have reached this stage with a mallet. The Scoop uses the more dense willow but this will not explain what you are saying so I think its a case of you misreading the response of the mallet. Try it in the nets, I'm sure it will feel fine.