>With the anchor letters, I find this trivial to read. It barely slows me down at all. Studies have shown that most people can read fairly easily when the first and last letters of a word are fixed and the inner letters are scrambled. Given the difficulty that dyslexics have, I suspect this isn't a realistic simulation.

That's only true when you've already reached a high level of fluency and are used to reading fast. You need to have a deep "predictive" knowledge of the language as well as a photographic memory of the shape of the words. That works well for literate native speakers but that wouldn't work well at all for a learner of the language, even at an intermediate level.

Since dyslexics have a hard time learning to read correctly, it's possible that they struggle to reach that level of fluency where you can just skim through text without paying attention to the small details of the spelling.

That's pure guesswork on my part though.