This is GameguySD achieving an earlier cycle for the boost through the ferdinands in 2-6. The clip through the moveable block ensures that early cycle. Furthermore, you can't wait at any of the lasers throughout the stage, otherwise you'll lose the cycle.

This is overall a rather precise trick that has quite a bit of RNG involvement in it. Couple that with the amount of precision required and you get a 2-6 that's not for the faint of heart and definitely not recommended in a Full game run, unless you're accustomed to resetting early game.