User blog comment:Sicarius001/Theory on Flash Step/Sonido Speed and Effects/@comment-10554972-20130726043516/@comment-4207271-20130729093004

I'm clumping them together because of the similar effects and because the effects are similar. If I knit-pick the finer details, it is likely people would either get confused or just skip it, and make judgments with no information.

As it is, the body learns to adapt to what is around it and affecting it. E.g. Uryu commenting that he can't follow Ulqi and Hichigo's movements with his eyes. Even at lower speeds, unless his perception had adapted to see even basic increases in speed, this feat would be impossible. This had been prevalent throughout the series.