That and he did flying seasons ago, effectively breaking that promise (or part of it).
That was a huge mistake.
Its one thing if Clark has no idea of his potential to fly. I think they could have stretched it out that way for a while. But now he knows he can fly but does not know how to. Along with the knowledge of Kara and other Kryptonians having flown makes him look slow. A late bloomer.
Plus the impact of his learning to fly has been nullified. They held nothing back in the effects when he flew as Kal-El. They could have hinted at it. Shown more as a blur. If that had been early in the last season, fine. With him actually learning to fly shortly after as a payoff. But now its been 4 years later and counting....
The showed all those sequences of him flying and then aspect fans to be impressed with running/blur effects. Its all just poor planning.