Mac (sometimes) notifies the non-admin user of an update, but not admin user

I have a Mac with one sign-in as an admin and one sign-in as a non-admin. For many years, the non-admin user will get a notice that one or more apps are ready for an update from the App Store, but as an admin user, no such notice appears. Just today, the non-admin got CapCut, Amazon Prime, and WhatsApp notifications sent to the non-admin account only.

This is not for EVERY update -- it's just once in a while -- but still, how can this happen? And even stranger is that this has been happening with me for many years, and many Macs. I just never asked about it until now!