We haven't heard of Ryan Higa before in our lives.
After watching his sketch we can safely say that the peg pants and LEX are totally different design.
1. The design of the peg pants and LEX is totally different. In the peg pants you attach the 2 sticks to your trousers and your weight goes right from your bottocks to the ground.
In the LEX, the shape of the exoskeleton follows the contour of your legs so the force distribution is not straight to the ground like peg pants. Actually the engineering challenge due to this (Anyone who study engineering will know when force is not applied straight it can cause all sorts of problems) and also making it fold-able is huge enough to warrant a patent in its own.
2. I'm sorry to report that Ryan Higa didn't invent the wearable chair. You can read the full history of them here. It's in an expired patent in 1979 (39 years ago). Even then it didn't have our folding mechanism!