You aren't really tapping on the top/bottom of the screen in an arbitrary way. There's a green oval indicator that you're on a call (or a blue oval if you have map navigation as I mentioned in my sibling post to yours). You tap on that indicator. It's been that way for years now. Perhaps it's not the most intuitive, but it's not totally unintuitive and it makes a lot more sense to tap an indicator object than to try swiping randomly.