No those are not quirks, there’s something wrong there. Going into Local View works every time, no matter if you’re in object mode or edit mode. You do need to have the objects selected, the ones you want to isolated. So if you want to go into local view with one part of the leg, you select that part and hit slash. If you want to go into local view with the leg and three other parts, then you select those three parts and then hit slash to get those three parts into local view. That works with how many other objects you need. So in other words, local view is like a parallel dimension where things you select get to go there and those that are not worthy stay behind.
