Ok, I definately tested this, and I can confirm that Dispel not removing Reflect as a retarded oversight.
However, I think I have an explanation.
Have you ever tried bouncing Holy/White off of Reflect and realize the Behemoth doesn't cast Storm on you?
Well, this is probably the issue that's being experienced. Whatever is being reflected is changing oh so slightly
(the game may be treated something reflected differently... but that in itself makes little sense).
However, I could not reproduce Dispel removing Stop in FF4ET (the spell should simply behave the same in theory).
I'm using the staff that FuSoYa starts with that casts Dispel (it works just dandy as an equivalent).
Perhaps the Stop effect didn't last long enough (I believe that the Spell Power is multiplied by the Spell Multiplier...
but I personally can't tell and haven't really tested that (nor the Hourglass items either... I never really use items in this game).

to item magic.