Extending that:

Have you ever moved inside someones guard with both feet push off the rear land the front foot adjust the rear foot (specially against a taller longer reaching opponent) and been smashing them up through the openings they leave between their arms as they react to you?

Or make em react even more: a light shove on an elbow as you go in makes their arm react the other way and you are in there and fire up the other side of that arm.

All require two feet, all are moving inside, no grappling involved.