Multiple uses of same internal function

The opr_sanity test checks the following:

-- Considering only built-in procs (prolang = 12), look for multiple uses
-- of the same internal function (ie, matching prosrc fields).  It's OK to
-- have several entries with different pronames for the same internal function,
-- but conflicts in the number of arguments and other critical items should
-- be complained of.  (We don't check data types here; see next query.)

Is this a leftover from the V0 fmgr days, or why is this not to be done?
In particular, using one C function to implement a group of overloaded
functions with different numbers of arguments seems useful.

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/