My new BTR15 is always showing PCM 192K when connected via usb-c cable to my cellphone regardless of what Amazon music says is plying back.

24bit/48K or 24bit/44.1 always shows PCM 192K

On bluetooth, amazon music tell me is playing 24b/192k or 24bit/48K and the BTR15 shows aptX 44.1

Even when playing very old MP3's I have in my cellphone, the BTR15 shows PCM 192K

It is something I am not understanding?