This is what it looked like pre-update.
Of course the iPad Air doesn’t have it, since the iPad Air doesn’t have a home bar. The iPhone X and later and the iPad Pro’s have the home bar, since they have no home button.
Yes, the bar always stays there.
Also I said it incorrectly, the “hidden home bar” mode only dims the home bar, it doesn’t completely hide it. I imagine that’s a bigger problem on the iPhone X where it would cover up the bottom menu row, but on the iPad it is completely fine like this.
Edit: I’m a bit confused haha. Referencing other apps, you can both make it so that the first swipe is ignored on the home bar (e.g. Procreate, Affinity Photo), and you can also hide it, which is most useful for games and video apps (e.g. Netflix). I think on the iPad Pro at least, the home bar doesn’t intrude much, so it can stay visible, and I also never accidentally swiped up on it.