I just put up a brief video comparing the efficiency of formatting a document with references in LaTeX via biber vs. using groff/troff via
Check it out yourself, but needless to say, groff gets the job done just as well in a small sliver of the time LaTeX takes.
refer as a preprocessor, simply reads a groff file, checking for inserts of
refer syntax and edits the stream adding the bibliography details from a database file that groff can read.
As expected in stream manipulation, it all happens basically instantaneously, much faster than TeX's method of puking out build files to be read by subsequent commands.