Not seeing the items that were higned, none of us can really give reasons for why another framer did what they did.
As for my comment, I just mean that some things are done out of ignorance. For example, many times customers would bring in artwork they had matted in their college art class, wanting to get a frame for their art. The artwork had hinging tape all the way around the artwork. When I asked why it was taped all the way around, they would tell me that their teacher did it that way so the artwork wouldn't have a gap between it and the mat. The teacher had never been informed about how to properly hinge artwork, and they were doing what they thought was correct.
Lack of education can be taught to the next generation.
So, as for the hinge being vertical instead of horrizontal, could have just been a case of an uneducated framer, doing what they thought was right. Also, while the tape is 3/4", you can cut it any length you want, so if they needed a small hinge they could have just cut it small.
But, remember, we are trying to answer this without actually seeing the size and weight of the art, or the size of the mat around the art. Blindly answering if this is correct or incorrect hinging tehnique (or was at the time it was framed) would be stupid.
I am sorry if my earlier post made it sound like I thought that a vertical hinge was never an option. I was just trying to give a reason for why someone would do a mount that a trained framer might question.