Motion Switch, is a move used by Hwoarang since Tekken 3.
The move's primary utility is to transfer between Left and Right Stance but can also be performed during Back Turn. When holding f or b during the stance switch, that movement will still be kept after the transition is complete (e.g: holding b during LFF b+3+4 then inputting 2 will result in Blast Fist (RFF b+2) coming out). Entering Right Stance this way in Back Turn also gives a small window for the Fox Step.