watchOS 6.1 and Apple ID

Yesterday I updated my AppleWatch series 2 to WatchOS 6.1. It asked me for my Apple ID password. Since buying it 3 years ago I don’t recall ever having to use my password (yes my passcode).
I also updated my wife’s AppleWatch and it hasn’t asked for her Apple ID pass.
Does somebody have an explanation?

No explanation, just that I didn’t have such an experience with my series 4 and don’t recall having had to do that when I updated to watchOS 6.0 earlier.

Could it have something to do with the App Store app now on the Apple Watch? I think I got the prompt on my Series 4 when I loaded 6.0.

No, but Apple’s operating systems prompt for your Apple ID password fairly frequently, so as long as a prompt is associated with something plausible, rather than an action entirely unrelated to your Apple ID account, it’s not worth stressing about.