This is really cool work. I like the fact that they are keeping it scoped to their needs, rather than building some general tool… but I’m also hoping more projects draw inspiration from this approach to language specification! If you’re interested in having a look at the current implementation you can find it on GitHub here.
I’m really interested in if this could enable some experimentation with different ways of presenting the formal rules. I much prefer the conciseness and precision of the formal presentation, but realise it takes a bit of work to understand how to read the notation. I think some of that is probably inherent to the domain, but if would be cool to consider how rethinking some of the design and typography could help with conveying the ideas more quickly.