Optional on purpose
Requiring process files would shut out illustrators who don't record their work, and it would reward whoever is best at faking files rather than whoever did the drawing.
So they're voluntary, and not having any is never treated as an admission.
Private by default
Process files often contain unfinished work, other clients' material, and personal metadata. They're stored separately from anything public, and only the artist and the reviewers on that case can see them.
The public listing shows that files exist and what kind they are. It never shows the files.
Every access is logged
When a reviewer opens a process file, that's recorded against their account. Downloading a copy needs a senior verifier and a stated reason.
What it changes
Process files are private dispute material. They do not raise a public score on the listing. Not having any is never treated as an admission.