Squeenix doesn't care about the lore much when it comes to balancing jobs ( "glaring" straight at you, WHM and AST) as long as it kinda works out for them, and even if it did, it could easily be explained by simply saying that were capable of making demi-summons instead of egi-summons just because at this point of the game, we have been exposed to garuda/ifrits/titans aether for quite some time now over all those encounters we had (without falling into possession). Which would not only explain the WoL point and title as the strongest SMN, but also the fact why other certain NPCs can only summon egis.
Or they just rework the entire thing from scratch. Also, were disgussing gameplay here so supplemental ressources are the last thing on this planet which should stop us from getting a properly functioning job.