The term Twine-Script is a bit like the term Motor-Vehicle, in that it describes a general class of programming languages rather than a specific programming language.
As each of the (currently) three default Story Formats has it's own syntax for it's macro language, and as each syntax is structurally different to the other two it would be difficult for a single language formater to support all three.
I believe that Snowman's syntax comes the closest to any of in-built formaters/languages supported by the Code snippet dialog, which would be either PHP or HTML.