Craftsmanship is a weak ability when it isn't brought into the game by the GM. Someone with a high Craftsmanship may be hoping for a bit more MacGuyver/A-Team construction-montage-related problems to solve, and even if they aren't getting them, it is easy to leave Craftsmanship behind. Craftsmanship has utility in all sorts of other scenarios, if the player can apply it creatively, if nothing else, to make Declarations. But without the GM playing to a character's strengths, certain character-defining skills *can* seem like a waste of points.
Which is not to say I perfectly challenge every player's top-tier skills on a recurring basis in my own games. But I try to.
So, all things being equal, it should be a Stunt to use Craftsmanship for the Lore requirements of Rituals. Lore is still representative of magical knowledge. If Craftsmanship is going to persist as a dud skill in your game, though, you may opt to give it for free.
One in-between option is to make sure the character has an Aspect that reflects their abilities, so it can be tagged for a Fate Point to give a +2 bonus to the Potion.
I do like the concept! Maybe later the character can purchase Channeling to summon killer Dwarven Scones.