Obviously Roglic does need "factoring in" because if Bernal attacks (& when he attacks), Roglic will go with him - whether WvA can follow or not.
If it's indeed true & WvA is doing Paris-Nice this year, I can see Jumbo using the race as a sort of live action exercise for the Tour, with Rog going for yellow & WvA green.
But the problem remains the same: Roglic needs the bonus seconds from sprint finishes, just as WvA does. So that automatically creates a conflict of interests on certain stages (namely punchy finishes).