What is the purpose of the format attribute autocad source filename - how can I expose it in Workbench

From Fmepedia

Q) What is the purpose of the format attribute autocad source filename - how can I expose it in Workbench?

A) It appears that autocad_source_filename was the original method of a user obtaining the source autocad file name. As I read it, we thought it was such a good idea that we created the generic fme_basename to cover all formats. I'm guessing the autocad attribute is still there for backwards compatibility.

So we won't be getting rid of it, but we won't be exposing it either: the recommendation is to use fme_basename instead