An outlier is a value that exists by itself among a series of much more consistent values.
For example, Plus Ultra tier characters (i.e., modern One For All users, All For One, Symbol of Evil Tomura, etc.) have consistently had Hypersonic+ to High Hypersonic+ feats, with Izuku having that nice Massively Hypersonic feat spliced in. A random FTL feat from a fodder would be disregarded, because there is nothing else to support it. The same goes for Plus Ultra tier characters.
"Natural progression" is not a valid counterargument. A jump from Massively Hypersonic -- which Izuku worked his off of to accomplish, combining the super strength of One For All, the momentum he built up with Black Whip, and the boatload of kinetic energy he generated prior with Fa Jin -- to FTL based off of a single feat is -- and, excuse my language -- ******* stupid.
Although, considering the route My Hero is going in, maybe FTL is a possibility.
Every day, we come closer and closer to My Hero becoming a supernatural battle manga.