I think there's a whole grey zone in between 'highly abbreviated text' and 'meaningful but not a language'. Steganography is one example. The difference between these and an encoded message, i.e a standard cipher, is that they are meant to facilitate communication instead of hinder it. Anything like music, coordinates, cooking instructions...
What these systems have in common is that they rely on knowledge that is expected to be present already with the audience. Knowledge about the notation system, how to play the notes, how to read the abbreviations etc.
If the text has a meaning and it resides within this zone, it will be the hardest to figure out because we simply don't have the knowledge the text expects from its readers. Perhaps the VM script has been designed to be read very quickly and easily, but we just have not been trained to do so.
What these systems have in common is that they rely on knowledge that is expected to be present already with the audience. Knowledge about the notation system, how to play the notes, how to read the abbreviations etc.
If the text has a meaning and it resides within this zone, it will be the hardest to figure out because we simply don't have the knowledge the text expects from its readers. Perhaps the VM script has been designed to be read very quickly and easily, but we just have not been trained to do so.