I'm beginning to think it has to do with the fact that Ramuh is acquired much earlier in the game and that early-game spells are supposed to be taught more slowly. The game makes you work hard and long to earn magical privileges this early.

Kirin is probably the best example. It teaches Cure at 5x and Cure 2 at only 1x. Compare that to the learning speeds of Starlet for the same two spells!

In order to be consistent with this trend, the game should have been designed so that Tritoch and Starlet are "supposed" to come well before Phoenix. That would mean no locks on the doors in Narshe, since you need Locke to open them and with Locke comes the Phoenix.

In order to avoid giving Fire 3 a special privilege, I would have added Ice 3 and Bolt 3 to two other late-game Espers at the 3x speed. Perhaps Alexander for Ice 3 and Odin/Raiden for Bolt 3?