The UESP has this about Keeper Carcette under "Bugs": "While Keeper Carcette offers expert training in
Restoration, the dialogue to do so becomes unavailable once your
Restoration skill reaches 50 or above."
However looking at the relevant dialog branch with SSEedit, I noticed that Dragonborn added Common-tier trainer Aphia Velothi to the conditions for
Restoration training up to 50, meaning that (AFAICT) to change Keeper Carcette one would also need to change Aphia Velothi (or, I think, edit Carcette so she uses a differently ID'd dialog branch).
So I had a look at the
UESP Trainers page & noticed that in pre-Dragonborn Skyrim, if Keeper Carcette is an Expert-tier
Restoration trainer, there wasn't a Common-tier one until Dragonborn, which while it wouldn't make
Restoration unique, is also not massively common.
Now I admit I didn't check her spells (mostly because it didn't occur to me, but also because I'm not sure how), but considering she is assigned to
Vigilant1hMeleeCllass. it makes sense she may not be overly brilliant at magic, even as a Breton.