"Learning history" is an interesting example.
As far as actually studying history goes, one needs to carefully examine real evidence, and restructuring the evidence in a way that is appealing to the observer's "style" is almost certainly damaging to its authenticity. To a large extent, user preference shouldn't even be a factor here.
OTOH, "textbook history" is, bluntly, mostly about memorizing fact/oids embedded in a highly curated narrative. That a dyslexic student has trouble finding the needle in the haystack isn't surprising, but to me it suggests that we shouldn't have students digging in haystacks in the first place. I'm certain that a more topographically-simple representation of the "historical facts" would be beneficial to all parties.
More charitably, though, part of the goal of reading textbooks is to develop textual parsing (reading) skills, so again if you take that away from a dyslexic student, what are you really trying to accomplish as an educator? Making them feel good? FWIW, I have a friend who was very dyslexic, but managed to overcome it in high school, not coincidentally while he was taking a series of relatively rigorous history classes that involved a lot of reading and writing--now he reads a hell of a lot more than me. YMMV, of course.