Sim.
A resposta está correta antes do texto que você citou:
These spells aren't separate spells you gain as a spell known from your spellcasting class, but rather mythically charged versions of spells you already know.
Ele também é definido no texto dos Mythic Spellcasting e Mítico Feitiço Lore habilidades:
To select a mythic spell, you must be able to cast the non-mythic version or have it on your list of spells known.