Even the most elaborate hydraulic systems, such as on sophisticated simulators, do not require anywhere near the room that the pit on this ride provides.
For the actual mechanics, no, but for the mechanics + room to comfortably perform maintenance, preferably without going into the realms of a confined space permit-to-work system... I dunno, I buy it.
As for the fact that such systems could be beside, rather than under, the track. Good point, though perhaps they want to keep the footprint small.
Also, don't forget that, though fairly accurate, this isn't going to be a 100% accurate animation - after all, it's missing many components like brakes, traction wheels, a method to lock the train in place etc. Mechanics in the pit would be left out, IMO.
Overall, I see where you're coming from, but I seriously reckon it could be legit...