It doesn't really make sense to optimize for screen space like this.
However, the teaching style along with a symbol alphabet that IS trying to solve for better legibility (without necessarily any allegiance to dyslexic fonts), could be pretty interesting.
In middle school when bored once I made my own symbolic alphabet, I found it really is extremely easy to learn a new symbol set for language you already know, so, changing away from the traditional symbols isn't even that massive of an endeavor.
I think they did do an OK job with using screen space well, but at the cost of legibility to a degree. That said, the more I think on it, maybe the author did too. Sure, individual letters aren't as legible, but the point is almost more that words become single characters, more like Mandarin. If those characters are legible, than it doesn't matter that the individual letters are not. If you don't know a word, you're already going to be individually inspecting the letters. (of course, it will still be mildly more difficult with dotsies)