This is a tension in the field of dyslexia/reading. Most academics in the US believe that dyslexia is phonological, not visual. If this is true, then visual supports like OD would not help dyslexic readers.
Many practitioners (and researchers outside the US) have a different view, which is that there are different strains of dyslexia, and some strains are more visual than others. I've talked with SPED teachers who laughed when they heard that researchers think dyslexia is phonological, not visual.
My own belief, based on years of working in the field, is that there is a significant portion of the dyslexia population who can benefit from visual changes to text presentation. This may be a direct symptom of their dyslexia, or it may be an indirect effect of (1) having dyslexia and struggling with reading, which leads to (2) not reading as much and having less-developed pathways related to the visual aspects of reading.
But given how dyslexia is defined as a residual category (roughly: a person who has a low reading level, not caused by visual impairment or deficits in general intellectual ability), it seems highly unlikely that no people with dyslexia have any visual aspects to their condition. There may be some, or even most, for whom the condition is phonological. But reading is visual in nature, so it would be very surprising if the group of people who struggle with it didn't happen to include anyone whose difficulties are visual in nature.
Of course, one can define dyslexia more narrowly (and some do), but schools typically don't. So if a broad range of kids are diagnosed as "dyslexic" in school, then it doesn't make sense for experts to proclaim "dyslexia is never visual, and people who say otherwise are wrong!".
My experience is based on launching a speed-reading tool (on HN, of course! [1]) that ended up becoming popular in the dyslexia and ADHD communities. It is a tool that is visual in nature, and I have gotten tons of emails from people with dyslexia who describe it as life changing. Some experts believe in what we're doing, but others are completely opposed to it. The dogmatism among certain experts conflicts with what I hear from people IRL, some of whom I have literally seen brought to tears by how effective our tools are. Even if what these people have is not "dyslexia" as defined by some people, they struggle with reading and are told they are dyslexic.
1: https://news.ycombinator.com/item?id=6335784