Thanks for the heads up.
OK so I completely removed my account from the xbox and did a system reset (but kept the games).
I used the app to set the xbox up but crucially this time when the system said it found old settings and asked if I wanted to apply them, I said no.
Now before I did this, my device on my microsoft account was pictured as some generic icon but it said Series x.
Since doing the above my device is pictured as a series x but is called xbox one!! It does have the proper serial number though.
However just tried remotely installing a gamepass title from the online Microsoft store and another in the gamepass app and a device is now listed - but its called xbox one. Selecting it does actually install the games to my series x though.
Weird!
Thanks for the advice though - it has worked a treat.
Mine shows as Xbox one which I've never owned