[GAMEPLAY] Leave Buster will not catch an idle Teemo with a Bami's Cinder passive

I watched a Teemo playing the top lane in a bot game until he had enough money to buy a Bami's Cinder. At which point, he headed to gromp, killed it and then sat idle next to where it spawns. Naturally, Gromp spawned again before Leave Buster kicked in and the damage from Bami's Cinder was apparently considered gameplay as far as leave buster is concerned. But since he was invsisible, Gromp didn't do anything to him so he could just sit there. Even if we killed gromp, it would spawn again in time before leave buster would activate.