I checked the box to allow GSX to control the graduated loading
We set that box unchecked on the PMDG 737 for a reason: PMDG clearly suggest in their documentation to not use or alter the fuel quantity using anything else than their loader menu. I'm not sure exactly why (better ask PMDG), but it's probably best to left it unchecked.
Regardless if that option is checked or not, it won't matter to the kind of truck you'll see, the only difference is that GSX won't control the actual refueling when it's unchecked, but otherwise it will look the same.
but don't see the worker hook up the hose. PMDG 737-900 NGX
That plane fuel point is not configured by default (we still haven't completed configuration for all supported planes), or you might have configured the fuel point too low.
If it's lower than 3.45 meters, which is the lowest the new fuel truck platform can go (taking into account safe clearance for the guy's head...), you'll still see the old truck.
On the PMDG 737, you might have to place the refueling point a bit more towards the outside of the wing, in order to reach that height.
