Yup, Marth has been doing this move since game's launch. Flying shieldbreaker. I posted about it here
http://smashboards.com/threads/best-shieldbreak-ko-option.435915/ "Best Shield break KO Option".
This move helps me get KOs at around 20%, because I can push them to the ledge from center stage, jump back, and easily and quickly space out the tipper hit.
Doing it this way also makes the Tipper even easier to hit, because the sliding forward motion makes the tipper range much larger.
If Marth gets a shield break on the opponent at 35% and doesn't get the K.O., it's because they simply haven't pushed the character to it's full potential - which is sad, because I see good Marths not take advantage of this all the time.
That's what I use it for. I also use it as a spacing mix up. The landing end lag on the move is minimal, and often the opponents won't know how to punish it effectively, and might leave themselves momentarily open. You just have to have time to charge it.
It can also sometimes catch someones recovery on to the stage, especially if they are out of jumps.
In any case, it's a one shot YOLO move that I use when I am entirely out of options, and hope that the other player messes up somehow.