When you're implementing a container format when a zip file would do, then you're doing it wrong. Which is why Microsoft now uses zip files for Word documents.
Bundling the dsp dumps in with the game rom is just going to cause complications, it wastes space & is bad documentation. He's going to make you download the spc rom separately still, my guess is that he must have run out of sane things to do & wanted some love for inventing a file format.