Official comment
You posted that on Christmas Eve, and if some other posts were answered, it may be that they were older and addressed first.
Regardless, the DJM-450 isn't designed as a MIDI controller for rekordbox, which is why nothing appears in that box. Yes, you can end up assigning things, but as you note, the controls you're looking for aren't configured for that type of input, hence the rotary not controlling both functions.
The MIDI functionality is still undergoing fine tuning and updating, we hope in future versions that the input control type for all MIDI controls can be changed, but for the time being, it's a bit limited.
Thanks for your feedback.