If you want yo play your rhythm externally you need to channelize track parameters.
For example track Level is CC95, so to affect Track 1 Level (assuming default channels are set )you need to send CC95 ch 1, to affect track 2’s level CC95 ch2 and go on.
Track Level is a track parameter, each track has a “Track Level” so it make sense to use MIDI channel to control them independently.
The Scene parameter is not a track parameter, it is a Common parameter, this means there isn’t a scene parameter per track but a single one for the whole kit. So it is pointless to use different channels to reach a single parameter.
This behaviour is like to have the Reverb Time parameter changing its channel depending on which track you are on.