Quinn's passive and akali's shroud

during a game the other day i was playing top as quinn vs akali and noticed that if quinn's passive was active before akali entered a bush it would give vision of her but if the passive was active and akali used her shroud then she would go invis

is this a bug seeing as quinn's passive is meant to grant vision if its on them before being out of sight?

i would have a video of it but lolrecorder is useless