"Huh. Figured that was a trick to it. Guess I oughta try it sometime."

As for the edge, Sans shrugs.

"The guys who can fly around here probably have a better way of checking it out than we do. But I could always tape a camera to some friends of mine and let 'em float around."

His 'friends' being the Gaster Blasters, but he's never shown them to Frisk before. At least, he hasn't. He's sure they've seen his magic one way or another.