Stuff like this feels weird at first but your brain gets used to it fast. I’ve switched to using the OpenDyslexic font on my Kindle and when you first see it, it’s very weird. But after using it for many months I don’t even notice that the letters are shaped differently anymore. Your brain will normalize the letters into looking like standard letters. I can only notice that the shape is different if I quickly switch between fonts. Using this has drastically improved my reading and attention span with much less fatigue.

I’m not sure if this bold method will have the same effect but if it does I think it would take some time to first adjust, and then stop seeing the bold letters as bold. In my experience with the OpenDyslexic font when you’re focused on the difference, it’s not helping, it’s only when you stop seeing it and are focused on the content that you realize you’re getting the content faster and with less work. Focusing on the letters themselves is doing extra work. If this method has utility it is in instant recognition without extra work. It’s not really possible to understand if it helps from reading a blurb because you’re going to be focused on the bold and not the content. I’d love to read a full book like this just to see how it feels.