President of Intamin told me all about it at IAAPA one year. Dudes a total legend. Supposedly it wasn't so much a danger to the human body, although it was uncomfortable, but it was stressing the trains badly and thats why it was nixed. Same reason I305 had its first turn reprofiled. Trains were coming back with soft melty wheels because of the forces and speed going around the original turn. Gotta give them credit for pushing the boundaries. Not even RMC will push the limits the way Intamin does when it comes to vertical g forces.
Honestly I'm thrilled that they're discovering these issues with Hagrid. That's how you know you're getting a solid, memorable ride. Looks like it will be more punchy than Cheetah Hunt, which is a poor example of an Intamin if I do say so myself.