That's a cool variant. There are dozens of binary json variants that are neither very good at optimizing feeding a 'sax-style' interface beyond a normal json file (they are all ok, solving the obvious issues that json has while parsing: base10 to base2 conversion, string unescaping, string length determination and whitespace, but none of them are excellent) nor being close to a dom-style representation to skip parsing for repeated simple queries. This is the second kind, and the first of them that I am aware of.
I like especially the realization that we don't need tons of number formats (duh). The beauty of json is its simplicity, so I don't get why people that try to invent a binary version of that add this complexity.