Yep - it's called melee attacks disruption in sandbox, but it seems that right now disruption is present only when you don't hit anything (at least with baseball bat), yet you walk unimpeded if you hit zombie, maybe disruption is set while recovering from attack, not during it. To be honest I thought it meant to buff knife combat, right now with bread knife you need only two hits to stunlock zombie and go around it to kill it whitch makes it a valuable weapon if your character is tired, before it needed three