Possible gameplay Bug

So how does camouflage works exactly? Twitch in this case. What is the time delay before champion intering zone and twitch actually being revealed? And does being in bushes does it effect being seen or not? If it's less then 0.5 s and being in bushes doesn't effect if twitch would be seen or not then if have a bug here. Can't check if it's reproducable right now but : I flashed on twitch and Tornadoed him as yasuo while he was in bush, when i heard sound of him being knocked up i placed a blue trinket there and moved into circle so i can see twitch. I was at the circle of twitch for more than 0.5 s but was being able to see him after he left bush more than 0.6 s.