Yes, showing you an advertisement for an app you've already installed is bad UI/UX, regardless of the reason why. On the publisher side, it's also a wasted ad i

Yes, showing you an advertisement for an app you've already installed is bad UI/UX, regardless of the reason why. On the publisher side, it's also a wasted ad impression. I don't expect them to know all the apps installed on my phone, nor do I think they need that much information to solve this particular problem.