No Diki, the Yamaha "on bass" function is not the same than the "bass inversion" function also available in Yamaha and Korg arrangers.
The "on bass" feature is determined in the Midi Receive settings and allows to trigger the bass note with an external controller, in my case the pedalboard. If the note matches the root chord that the style is playing you get the regular bass pattern if, let's say, your left hand is playing a C chord and you press a G note on the pedal the arranger keeps rhytmicaly playing the G note.
I hope I made myself clear enough in English.