I think that is what has always been there.
In Nautilus (file manager) under Gnome3, if I right click a .doc, it shows as libreOffice as the 'main' associated helper app (it has Dia also associated). It also shows that under the properties tab. I have been using .docs for ages without a problem within the 'desktop' environment.
My only problem is the association under Firefox. I'm still getting as per the attached. Even if I select the 'do this from now on' (ie open .doc with libreoffice), it reverts back on next open.
Stop press. I have just tried on two sites, on both the files are shown as a .doc's. On one site the opener is then correctly identified by FF as libreOffice, and on the other it appears as unknown. So the implication there to me is that the .doc on the second site (that is the site that prompted this thread in the first place) isn't really a .doc (does it work by suffix association or by the type of the file?).
I get these two conflicting open dialogues - so it looks like a problem with the files on the sites, rather than association my end?