Currently the description of the user setting to disable/enable the Popups extension[1] is page preview centered : Page previews (get quick previews of a topic while reading a page):
Since that setting currently disables/enables both, page- and reference-previews we should think about changing the text to reflect that.
Note:
This probably only makes sense, when we decide on going out of beta with this and to keep one setting for both. Currently the feature is completely hidden behind the beta switch.
[1] as found on https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering