Fairly certain, as I hadn't downloaded anything on my phone when away from my PC that would have produced a notification to mirror. Also, sorry, I should have mentioned from the start that I typically run my phone in Do Not Disturb and Silent to minimize any notifications whatsoever.
On further digging I did notice that it looks as though the files mentioned in the notifications may have been downloads, but from literally years ago in, I think, every case (e.g. from 2018!). I don't think I even had Connect installed back then to have caught those notifications. 🤨