“Complete his training” is relative. If he’s already enough of a badass to freeze someone in mid-air with his mind at will,
It could be that little trick wasn’t even a Force power.
Maybe it was a piece of technology that created a "stasis shield " around an energie beam.
Maybe is was a glitch in the edit, nope it was just as ridiculous as the rest of the film. I just got over prequelitis, now suffering severe sequelitis.