I would think so, or by taking cross sections. Its hard to believe they have some miraculous geometry that needs guarding anyway. Maybe they are trying to dissuade people who might try to 3d print an impeller.
3d models for industrial fan manufacturers (Sanyo,NMB) are widely available.
They make sense when you consider that 'on detector' electronics has all sorts of constraints that FPGAs cant compete on: Power, Density, Radiation hardness, Material budget.
-48 to 48 claims something like 97% (load dependent of course). It also needs to arbitrate between two input supplies for glitchless redundancy, plus have PM bus and other spec mandated stuff. There is no technical reason why you cant go -48 -> 12 as you state with good efficiceny, but we cant get hold of a part that ticks all the boxes.
Horrific performance by my definition would be 48v to say 1v. We only realistically use buck topologies for POL supplies. Such a ratio is really bad for current transients, not to mention issues like minimum on times for the controller.