I got confirmed that on 2F, the Ulti agent at check-in is supposed to let Ulti pax bypass security queue if any which might be a good time saving option

Regarding (pre)boarding, to me there's nothing very clear and I might understand it's tricky to organize from AF perspective.
The only way to get pre-boarding is to show early at the gate with a 99% probability of waiting either at the gate or in the footbridge
The only way not to wait the last moment to board
But I do not see how operationally it would be feasible to mix both preboarding & no waiting

What I would find interesting is for AF agent at boarding to inform AF agent just before finishing boarding so Ulti pax could wait as less as possible
But that implies for AF staff on board to reserve some luggage space to make sure it's OK to board last