I think the developers assumed you would try mastering spells as soon as you get them. You have Ramuh very early on in comparison to Shiva, Ifrit, and Maduin. Really, if you just think about the order you acquire them, most of them seem consistent with chronology.

I do see the problem with Maduin but then again, you can learn the weaker spells from Ramuh, Shiva, and Ifrit then once you learn those you can switch over to Maduin and have less time to learn the level 2 spells than you would had you waited for Maduin. Phoenix, for all intents and purposes is one of the few Espers I feel the developers felt you would last attempt considering how nasty the Phoenix cave is and you need a lot of your party members to traverse the cave properly. So it doesn't really negate Starlet completely.

Not to mention you can have two party members learning the same spell and then switch over when they master the desired spells.