Wrong Apple ID in AppleTV's App Store; how do I change it?

I have an Apple TV 4k [model A1842, tvOS 14.7 (18M60)]. The "Current User" is 'Steve' (namely, me; thus, my Apple ID is "current" and happens to be the Default User too). My wife (Jill) is an Additional User - not currently logged in (or at least that's the way I think about it - maybe I'm wrong? If she is listed as Additional, does this mean we are both simultaneously logged in?)

If I open the App Store, a certain new (-to-both-of-us) App I want to download only & always shows my wife's Apple ID by default and I cannot change it to my (the current) Apple ID. How can I do this? I have tried a factory reset of the Apple TV, but this App only shows or allows my wife's Apple ID.

Question 2: I obviously don't understand how Apple IDs work in an Apple TV. I was thinking that the Current User's Apple ID is what would always be shown in the App Store. This is obviously wrong.

Any explanation of how to both fix this (e.g., use my Apple ID for new Apps) and how to think about this (dual log-ins or not) would be helpful.