Yes, the header of a romc compressed file stores the file size and the compression type. I'd be interested to see if this works for injection, because then you won't have to bother with a compressor.
I'm telling you to try it in VC titles that do use romc compression. When I looked at the decompression code it accepted all of these types, so I expect that it will work with type 0. They probably wouldn't have used it once romc was available, to save bandwidth and flash space, but I think it is supported.