Probably only as a double-check if the iPad detects that it's been handed to a different person without being locked. In most cases you'd want to continue under the assumption that the user who unlocked the device wants to open things as themselves.
Mind you, the Switch has to do user-switching only at app startup time, because it's an effectively single-tasking OS. Given that you can be running tons of apps (and instances of apps) at the same time on an iPad, there are many other UI possibilities that synergize with an explicit user-chooser. Examples:
- You know the app groups in the new macOS/iPadOS? Imagine a user profile as an app-group-group (in iOS) or a group of spaces (in macOS.) Do the slow-swipe-up-from-the-bottom thing again when you're already in the app chooser, and you get the profile chooser.
- Some gesture you can do while in an app, that means "give me this same app, but viewed as a different user" — which is like a retroactive version of the Switch user-chooser thing. If other users already had the same app open, it'd work like Expose/Mission Control for seeing what their instance of the app looks like. And, as an optimization, apps that detect that you've user-switched away from them soon after launch, when they're still in their toplevel view, could take that as a signal to quit (as they'd assume that you just meant to open the app as a different user.)
