switch-to-buffer in minibuffer

[Chong Yidong]

Regarding this item in etc/NEWS:

  *** Operations like C-x b and C-x C-f, which use switch-to-buffer, do
  not fail any more when used in a minibuffer or a dedicated window.
  Instead, they fallback on using pop-to-buffer, which will use some
  other window.

What does this mean?  Naively, it seems to be saying that
C-x C-f C-x C-f will do something new, but it instead gives the same
error as previous versions of Emacs ("attempted to use minibuffer while
minibuffer is active").  So what's this about?