Why doesn't Ignite reveal Pyke?

Ignite reveals people. However, if you Ignite Pyke and he uses his W, he is able to go fully invisible. While Ignited.

This is very unintuitive. You'd think "Pyke is low, he's about to get away and heal, I will use my summoner spell that's only two functions are to secure kills on people that are low and keeping them from healing", but Pyke is able to turn invisible and start healing with the Ignite on him, so you can't actually kill him with it.

Is this a bug, or a balance decision? I'm pretty sure a reveal is supposed to make camouflaged champions visible, right?