Regardless of archive file path defined under Settings > Publishing > Archive Mapping,
using in the context of invariably produces the string, "index.html".

I have not checked to see if the same problem exists for individual, daily, weekly, category or user-defined archive types.

That sounds correct if your archive mappings all end in index.html. That tag returns the filename itself, not the full path.

http://www.sixapart.com/movabletype/docs/3...rchivefile.html