Enkidu you are correct, lateral or angular movement is in fact your friend, in this and in almost ANY type of combat. As a rule in Tang Soo Do straight in and out attacks and defenses are not encouraged and in fact the originator of TSD, a Korean with a distaste for the Japanese, designed the art as a weapon to be used against hard Japanese styles or as you put it "Rock 'em Sock 'em Robots." As was said in a previous post the fighters in the vid were very young and somewhat inexperienced. Although a Hop Side kick can be used offensively it is much more effective as a defensive attack when an opponent is closing or attempting to close on attack regardless of their footwork or the direction they are circling. Correctly done a Hop Side kick telegraphs movement very poorly as it is an instantaneous exchange of foot position accompanied by a simultaneous kick, most time the kick has hit before the opponent realizes what the kicker has done. I agree that many martial artists and instructors appear to ignore a great deal of the overall equation where footwork is concerned, I also see as idiotic the concentration on the Sport aspect of a martial art, making it a martial sport not an art of combat.