It surprises me that there isn't a requirement to hold the stick constantly in position for a period of time to disconnect the autopilot, not simply for a knock to do it.
Perhaps that is because you don't understand the design logic. There are 3 ways to disconnect the AP. Stick movement is the least used, it is designed so that instant response is given for an urgent requirement to uncouple the AP and manoeuvre the aircraft immediately in non-normal situations where a time lag could be detrimental. i.e I need a response NOW, not in a little while, when you are ready, please.....