I believe that what Aresaka is referring to is that there is a split-second between when Flare casts and when it applies AFIII, much like Fire spells have. During that split-second, if your timing is right, you can get a tick of UI to go off, meaning you go from 0 mana to (1 tick of UI regen) mana and can thus continue your rotation with no downtime. Although, if this is the case, I see no reason for the Convert in the rotation...