I have been getting this as well. My guess is that it's related to the ability of M1 macs to run iOS apps and App Store preferences.
I am running Big Sur on an Intel Macbook which does not support iOS apps
When I have the option App Store > Preferences > "Automatically download apps purchased on other devices" enabled and I purchase a new iOS app via the App Store on my phone, I get a few notifications on MacOS for a few different iOS apps stating they can't be downloaded. These are not necessarily for the app I've just purchased on iOS, I think any purchase simply triggers them again. I assume they are apps that have opted in to support being run on M1 macs.
When I have the option App Store > Preferences > "Automatically download apps purchased on other devices" disabled and I purchase a new app via iOS, I do not get notifications in MacOS.
Re-enabling this option, and purchasing a new app, I get the notifications again.
I imagine it's a bug that will be fixed at some point. In the meantime, the work around seems to be to disable that option (that's what I've done).
Note: I'm currently running MacOS 11.1, but looked through the 11.2 changelog and don't see mention of this particular issue so I suspect it's still present and Gary Makin's comment above I assume is related to updating to 11.2.