So anyone know why it works and what the window is for executing it?

Is the PC/PS1 your talking about from here The window is pretty weird its mostly just to move foward in a certain angle and then just keep jumping to the right

No there's a cutscene at the end before the portal, it does not play if you do it at a specific angle but really I'm just winging it

If you are still curious, you have to get the escort stuck on the log before the end so the cutscene will not play. Cutscene begins when escort reaches up the hill