I tried looking through some of the spec samples, and it was not clear what the "language" was or that there was any syntax. It just looks like a terse spec.
In my building and research of Simplex, specs designed for LLM consumption don't need a formalized syntax as much as they just need an enforced structure, ideally paired with a linter. An effective spec for LLMs will bridge the gap between natural language and a formal language. It's about reducing ambiguity of intent because of the weaknesses and inconsistencies of natural language and the human operator.