lvl 90 spirits summoned by a lvl 90 summoner currently cast spells as they are a level 75 blm.

Example
Thunder spirit lvl 90 casts
Thunder IV, Burst or Shock.

It does not work to try and process yellow weakness on Abyssea mobs since it is missings several spells.

And does not work as a DD spirit.

A level 90 spirit in theory should be casting
thunder IV, Burst or Shock.

ok.. ops lets look at Earth spirit.

Earth spirit will cast at 75
Stone IV, Quake, Slow, Rasp

Earth spirit at 90 should cast
Stone V, Quake, Slow, Rasp, Break

Quake II is a merit spells and spirits have never had merited spells.
Stoneja is an AOE spells and spirits have never had AOE spells (other than sleepga for Dark Spirit).