Overloading methods in R

I guess the context says you cannot have something like this in S4:

setGeneric("testFun", function(...)

+ standardGeneric("testFun"))

But what is wrong with:

setGeneric("testFun", function(object, ...))

Keeping in mind that 'object' is the actual instantiated object of the
class which you wish to operate on.  I guess I don't see how that aspect
is a problem?