For a lot of people knowledge about experience is gained by first having experience and then reflecting upon its details. However Mary's knowledge must be so throught that he must know the qualia minutia pretty accurately. It would seem she would be in a position to be able to hallucinate color before actually seeing it.

What is unintuitive about Marys position is that usually studying books doesn't develop any good deep rooted intuitions how things work. Usually being able to pass a test on the subject is sufficient bar for having ingested the material. Even in mathematics education there is a focus on "having routine". That is you need to actually do calculations to really understand them. I think this is aknowledgement that part of the understanding that is targeted at achieving is very lousily transmitted by prose.

Say that Gary knows perfectly that needles hurt but has never been injected with a needle. When he gets his first vaccine and it is just as he expected does he gain new knowledge from it? Is it consistent to answer differently for Gary than for Mary?