I guess Mirage probably means that there isn't a luck stat that has an influence. I.e. luck is the same for each player.

It's unlikely that "luck" is weighted in any way that isn't relatively transparent. For example, there's no hidden luck stat given to a character at creation that influences random number generation. (Its unlikely anyway). But treasure hunter does increase the chance of an item dropping, like BLU gloves increase the chance of learning a skill.

It's all pseudo random number generation, but they could increase the 'success' range of RNG when learning blue magic to make it easier.