I think your guess is probably correct, but only the empeg people
can answer definitvely.

There's also an interesting new type 0x05, CHUNK_UNTARDRIVE0.
I keep meaning to try it out but haven't got around to doing so yet.

I hadn't seen Sven's upgrade splitter when I wrote mine, which
knows how to handle both these types, and, indeed, any other type.
See http://empeg.org.uk/up.html