Quote - DAZ has something called "Extensible Parameters", unfortunately I have not been able to find any technical info on it, though is seems to relate to the readScript method mentioned above.

EXP is mostly an organising convention for the multitude of readScripted files that contain the channel and group information.
As I mentioned DAZ have chosen to use an "updater" program which gathers a list of files and writes a new pair of "master" files for each body part.
The simplest way to see the details is to download either or both of the V4 and M4 Base figures.

Dodger's Aeon figures (Anna et al) were organised similarly (less indirection IIRC, updates supplied the new "master" files, which was OK as there wasn't any expectation that anyone else would provide updates).

Tiny's "Furred Cat" also made use of readScripts to reuse common sections of CR2 to avoid bloat.