That's indication is just a texture, it doesn't have anything to do with the kind of fuel used, we might add a repaint for it, saying Jet A1, and display one or the other depending on the Fuel type in the airplane, but that will be only a cosmetic issue, like choosing an operator over the other.
What I think you are missing here, is you probably were expecting a Fuel Hydrant or a Tanker, that doesn't have anything to do with the Fuel Type, it's ONLY because, as already discussed in so many threads, the Tanker requires being on an APRON AND having a refueling point higher than 3.00 meters from ground, while the Hydrant requires being on a GATE, and having a refueling point higher than 3.40 meters from ground, that's the lowest the platform on each vehicle can go, so you won't see the Hydrant on a 737, because the wing is just too low, so that vehicle will appear instead, which has no crew animation.
On Aprons, you might get the Tanker because ( depending on airplane *weight* which affects height from ground ), the refueling point might just be higher than 3.00 mt. to call the Tanker and, if you want to use the Tanker even on GATES, you can just disable "Underground refueling" option in the scenery customization page for the affected parking spots, so those will always use the Tanker.
As already confirmed multiple times in other threads, we ARE working on a completely new animation for the fuel truck, which will use the large spooler with a cable extending out and under the wing, which can be accessed by the crew without a raising platform, just a ladder step or, in case with planes with very low wings, like the MD80, just by standing up.
