Tsugi ashi- if left /right foot is leading ,the opposite foot keeps behind leading foot.To advance push with back foot , sliding lead foot .To retreat [move backward] push with front [leading foot]
and slide rear foot to rear.As far as it being a sliding footwork , yes it should be so. Tsugi ashi foot work is also used in Bokken suburi [cutting forward [advancing ] linked with cutting while retreating] ie a double shomen movement .
i was about to say the same thing, joe. not so much dragging the rear foot behind the front, but pushing the body forward.