This may not be considered a "bug" per sey, however it is an odd concept I noticed.
Kaustra and Embrava are level 5 spells that can only be cast while under Tabula Rasa. However, when SCH is a sub job, that spells are present in the spell list however the spells are always uncastable. As far as I know, there are no other similar situations in the game where a spell is listed and there is no way to make that spell castable.
The spell does meet all the criteria of being "allowed' to show up in the list but it seems wrong that an uncastable spell should be there.
I'm not sure the Tabula Rasa idea is the way to go with this spell. I know the intent is to make the spell very hard to cast. Maybe a good alterantive would be 30% of max MP as well as all availible strategem charges be availible and used on casting.
Its not entirely unreasonable to remove the Tabula Rasa condition as, while SCH is not BLM, it is bsically comerable to any higher tier BLM spell that SCH has no access too (I.E. Burst II, etc.)
Just a thought.