Grover’s Expedition

Will banning these spells on the map still allow them to be learned through magical omniscience?

Or maybe it's simpler to disable this perk altogether (though then this map would turn into a mod).
Alternatively, you could give the main hero a starting perk that prevents entering the Skill Tree (e.g., a "mana regeneration" perk), but in this case, the map would need to be made without a mentor (so that the interfering perk cannot be transferred to the mentor).