Why filenames instead of rolenames in snapshot?

Previously, we used to allow metadata files nested inside directories, which explains the following text in the specification:

   METAFILES is an object whose format is the following:

       { METAPATH : {
             "version" : VERSION,
             ("length" : LENGTH,)
             ("hashes" : HASHES) }
         , ...
       }

   METAPATH is the file path of the metadata on the repository relative to the
   metadata base URL. For snapshot.json, these are top-level targets metadata
   and delegated targets metadata.

However, I don't think we need METAPATH anymore. Instead, all we need is to list valid targets rolenames instead, correct?

Start with section 4, “Document Formats,” of the linked specification and review the METAFILES and METAPATH definitions in the snapshot format. Determine whether snapshot metadata should list repository file paths or valid target rolenames, then update the specification once that format decision is agreed.