In regards to the kick glitch, isn't that pretty similar to how the kick in Warband worked? Attacking while you're still performing the kick animation causes you to just drop your attack, but waiting until the animation finishes allows you to attack. The difference between Warband and Bannerlord's kicks is that it seems in Bannerlord the kick pushes your opponent further away and doesn't stun them long enough for a follow-up attack (which makes it pretty useless).
I think the period that you cannot attack right after a kick is to prevent baiting your opponent with a missed kick and then attacking them when they try to punish you for it.