Yeah it's a glitch for sure, or at best an oversight in testing for unintended control. It's a really well timed fast swap of z to stomp and a to flutter and the forward momentum kicked up by each motion can keep you going beyond the starting inertia. I've tried this originally seeing the megahammer boss stage and I didn't even at first realize that Z stomp was being used so I couldn't stay up and had to do it the normal way. That video I annoyingly didn't watch on topic open here of just going up the mountain made it damn clear as they totally show you how it works without writing in those dumb youtube notes text detailing it. I'm not so certain I'd want to abuse the game like that as I'm doing fairly well as is right now with 54 stars nabbed and up in world 5. I just need one more, had to stop last night doing world 1-2's speed run (those clocks are murder) or I'd have 55.