If you apply a modifier like S, U or K during hitstop, the movement isn't added to the object. Other effects of the modifier are applied however. For example, parry and uppercut will unground but won't change velocity. This is frustrating as spaming structures like ball or disk mess up combos, parrying and rts (hold breaks immediately because velocity is too high).

My assumption for why is that velocity is saved as a variable at start of hitstop, velocity is set to 0, then velocity is set to variable previously set. If my assumption for how hitstop works is correct, this could be fixed by making it so velocity applied during hitstop is added to the variable.

Edit: Added video example, hold is applied during hitstop, meaning velocity doesn't reset and hold immediately breaks.