Why is my iPhone 15 Pro playing some Hi-Res tracks as Lossless on Apple Music?

Hi, firstly apologies if that has been addressed elsewhere, I have searched and can't see anything for this specific issue.

I have just got an iPhone 15 Pro and was looking forward to being able to connect to my Chord Mojo 2 with USB-C, however something weird is going on with Apple Music on this new device. If I choose a 'High-Res Album', a lot of the tracks are just playing as Lossless, not Hi-Res.

Example - the new Beatles Blue Album - Strawberry Fields Forever plays at 24-bit/96kHz on MacOS and on my old iPhone 11(!!!), but on the Pro it's stuck on Lossless 24-bit/48kHz. Skipping through the album, some tracks play at Hi-Res, some play at Lossless. On my other devices, it all plays at Hi-Res.

I've tried deleting the app and reinstalling - no change.

I've tried un-syncing and re-syncing my library - no change.

Has anyone else had this issue and managed to fix it? Any help would be appreciated.

[Re-Titled by Moderator]