There is precedent for the 76" max height, ultra-irritatingly. Intamin has annoyed me with this for more than 15 years now.
Superman at SFNE was the ride that taught me I would sometimes have to wear the thinnest-soled shoes I own and slouch a bit if I wanted to ride certain rides, and that started in the early 2000s. Same max height there, 76". They might have made that change after the fatal accident, or maybe the ride opened that way. Don't remember. But they had a little swing-stick thing mounted at the queue entrance, 76" off the ground, and for a time there was an attendant paying attention to it sporadically to make sure no giants got aboard. If the swing-stick hit you in the head, you didn't get to ride.
VelociCoaster, as far as I know, has no such max height, leading me to suspect it's not about seat or restraint configuration, nor about reach with respect to components or corners of the rolling stock itself. Of course, the vehicles could be different at Universal in a way that establishes a key difference in this area. I really have no idea.
Some other possibilities:
- The max height policy is optional, perhaps suggested rather than required by Intamin, leading to the question of why to have it in the first place
- There is a simple difference between what the two parks' respective insurers are willing to allow, perhaps in connection with the item above
- It's a reach issue, lateral or upward, regarding the proximity of stationary trackside (or overhead?) items, probably net of a very conservative safety margin juuuuuuust to be sure. While I'd be surprised if Intamin cut the design too close in the one most obvious place on the ride -- especially given modern design tools -- it's not like there is no precedent there...
Maybe another reason - they calculated the heartline forces using an average of guest heights; anyone too large could experience forces directed at the extremes of their bodies that otherwise wouldn't be experienced by shorter guests fitting within the average size range.