One annoyance of ensure-generic-function-using-class

Hello,

there is something annoying with ensure-generic-function-using-class. The MOP specifies that if the :generic-function-class option is not provided, it defaults to standard-generic-function. While this makes perfect sense when the generic function doesn't already exist, it seems to also apply when it does.

As a result, if you want to call ensure-generic-function on an existing generic function using a different meta-class, for instance like this:

(ensure-generic-function gf-name :generic-function-class (class-of gf))

This is a bit annoying, and I don't understand the rationale behind this, if there's one. Why not defaulting to the existing generic function's meta-class?