Thin Air not functioning as the tooltip implies

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Frequency: Always
Class/Level: 71+ (Bozja), White Mage
Area and coordinates: The Bozjan Southern Front or Delubrum Reginae or Zadnor
Steps:
1. Use Thin Air to nullify the cost of the next spell or Lost Seraph Strike cast.
2. Use Lost Chainspell to increase the damage of the skill while also increasing MP cost by 30%.
3. See that Lost Seraph Strike costs 1500 MP to cast despite the MP cost being nullified by Thin Air.
4. See that all other spells also cost 30% of their MP to cast despite Thin Air being active.

This also applies if you use Chainspell first then Thin Air, and obviously doesn't apply if you have Spirit of the Ordained up due to that nullifying the MP cost increase from Chainspell.