"Boast Busters" would seem to suggest otherwise.>Spike: Twenty-five, Twilight. Twenty-five different kinds of tricks and counting. I thought unicorns were only supposed to have a little magic that matches their special talents! >Twilight Sparkle: True, for ponies whose talents are for things like cooking or singing or math.
While neither Spike nor Twilight outright say that other unicorns learn "spells", the context makes it pretty clear that most unicorns intuitively figure out some basic spells associated with their cutie marks but never/can't progress beyond that, with ponies with Magic as their special talent being an exception.
So a unicorn with a special talent for baking might intuitively figure out stuff like a heating spell or a flavoring spell. If Twilight is considered highly exceptional for knowing twenty-five, then most unicorns probably only learn, say, six or seven.