Re: debugger with pop-up-frames non-nil: keeps creating new frames

[Richard Stallman]

    And, yes, I think the default value for `display-buffer-reuse-frames' should
    be `t'. People upgrading from versions of Emacs that don't have this
    variable will expect more or less unchanged behavior without having to
    explicitly set this variable to `t'.

As far as I can tell, the current default of nil provides unchanged
behavior.  The change was in version 1.302 of windows.c.
Why do you think it is the contrary?

(Such a change could be an improvement nonetheless.)