Mario is supposed to be small, and waits at the bottom until an icicle drops a vine from above. Spike traps make it so you cant climb the vine with diagonal joystick movement, and it shouldn't be possible to do a buffer jump since the vine won't come down for a while.
I'm not an expert in tech so if anyone manages to break it let me know!
Looks like you can't initiate a crouch with a buffer jump, so if you move the fishbone above the hidden block, and force Super Mario out of the pipe, it should be cheese-proof. If not, maybe that's more impressive than the level itself :3