I think that this is an example of where, although the current situation in the game is not entirely realistic, it does make the games easier to comprehend for beginners or non-aviation enthusiasts - it’s easy to understand that GA aircraft use Avgas and commercial aircraft use Jet A1 without having to either zoom in/listen to each GA aircraft to try and figure it out.
Equally, explaining that some propeller aircraft use Avgas whilst others use Jet A1 (because some propeller aircraft have piston engines whilst others have gas turbines) to non-aviation minded people is not easy.
In the current game, you can entirely separate Avgas and Jet A-1 fueling and equipment and capacity planning because you can forecast your GA and commerical traffic - it would be much harder to forecast Jet A-1 needs if you didn’t know how much jet GA traffic would be using your airport on a given day etc.