It appears to me to be "yet another" because the length before the string approach is usually referred to as a b-string.

windows (for example) has had a comprehensive b-string library (type is called BSTR) for about 20 years - due to it's age and provenance it has the downside of thinking a character is a 16-bit value...

You're right, sorry. I only scanned the document, saw the struct, and closed the tab. The way you use a header before the data is similar to how Ruby represents its strings internally.