By default, Filently only accesses the documents you want it to organize, plus your Drive metadata: file names, file types and folder structure. Filently analyzes the content of these documents to understand what they contain, give them meaningful names and find the right folder. It can’t access the content of your other files.
Full Drive access is requested only if you turn on inbox folder watching, so Filently can detect new files in your inbox folder. Even then, it only processes the files that land in that folder.
Google’s consent screen mentions “delete”, but Filently never deletes files. It only renames and moves them, and you can undo every change from the Activity Timeline. You can revoke access anytime in your Google Account. Which permissions Filently asks for, and why.