Yeah, the straight leg (if we're talking about the same thing) glitch happens when the game thinks you're going to land on something, but you don't. It starts the landing animation, straightening the legs, but it doesn't finish where it thinks you should, hence the legs sticking out too long.

It happens mostly when you ollie over something tall and barely clear it. I dont think there's a way to make it happen at will unless you maybe drop an object and ollie over it? As far as I know though, it doesnt help you land bigger gaps.