Probably right. Knee stomp doesn't KO fighters. But while a boxer is dealing with it I have my chance to punch. When he starts boxing again I may grapple. I can punch and need to punch, but I will always avoid the opponent's 'comfort zone'. That is my point.To effectively use the knee kick you really should be able to handle the hands exchange.
Additionally, knee stomp doesn't KO fighters because both are usually well trained and it is not meant to break the knee. A straight knee stump in a stand-up guy (self-defence scenario)... I guess it has a different effect.