I think you’re definitely correct in critiquing the language commonly used when telling the thought experiment! Does Mary “learn” something new? By my working definition of learning, no she doesn’t. “Understanding” is a better word, but I feel even that is a stretch. I think all we can confidently say is that Mary “experiences” something new.

Kinda like if I watched and learned all about Cajun Creole cooking and knew about all of the techniques, dishes, and spices. Then I go to New Orleans and actually taste the authentic Cajun Creole food. Did I learn something new about the food? Unless I had an unknown food allergy, I would say no again. But I certainly would have had a new experience! Maybe learning whether or not I actually like the food.

One point to raise in my alternate thought experiment above is that all of the things I mention that I might learn from that experience involve an interaction between new food and my particular internal chemistry and tastes/preferences. Things that I would necessarily not have known unless I actually eat the food. I guess it’s theoretically possible to know one’s gut chemistry well enough to know how something would interact, but I digress… I’ve rambled enough, but I think there’s something there to help delineate knowledge from learning from understanding.