Possible Kindred bug

So I was playing around with kindred with the AI bots and found this out. I dont know if its intended, but I could not find anything about it.

I mark the enemy Master yi and was successful in killing him proc-ing my passive and gaining a stack. Passive went on cooldown and everything. I assume once you successfully kill someone marked, the mark should go away forcing you to mark another target. However, in my case, Master yi Bot came back alive and was still marked and also gave me another stack upon killing.

Possible bug or intended?????