Prior to iOS 11, the OS would quite often ask for your Apple ID username/password by showing a popup regardless of whether you were in another app or Springboard. Since you don’t know what the hell’s prompted that request, it was noted that this opens a vector for phishing [1] and it conditions users to blindly put their password into anything that asks.

I wonder if this is an attempt to fix that gone wrong.

1: https://9to5mac.com/2017/10/10/psa-apple-id-phishing-attempt...