From BMS Manual (in your :\Falcon BMS 4.32\Docs\Falcon BMS Manuals folder) p139:
Tankers de-aggregated in 3D world will now fly a two minute holding pattern anchored on their first target waypoint
when there are no receivers in their refuel queue. At typical speed/alt for tanker flight plans this is probably a 15-18nm
oval from apex to apex. As a result the tanker should most of the time be closer to that first target waypoint where he
will anchor in the holding pattern until receivers come along at which point he will fly the full track pattern.
Since the aggregated tanker flies the full track length all the time in 2D world, it is possible that when he de-aggregates
for your flight that he’s not in the holding pattern. If he has no receivers in tow he will try to enter the hold if you don’t
get there and ask for fuel before he reaches the anchor turn point. This may be useful to you depending on the
geometry: it may be more efficient to fly an intercept on the tanker’s anchor point and only call him for fuel once he
enters the hold. Certainly if you join and call for fuel as he turns outbound again from the anchor point you will have
the longest straight and level segment of his track to try and grab fuel before he turns again.
The last bit I put in Bold is the top tip here. If you wait until the tanker has almost completed his turn outbound from his anchor point you will find he is much more likely to fly the full track pattern. It doesn’t always work but it’s the best chance you have if you’re still a bit nervous about topping up in the turn.