Fx 37.0.1, Fx 31.5 ESR, Pale Moon 25, Sea Monkey 2.33.1, Thunderbird 24.7 on Windows 8 Pro and Win 10 Preview NONE can get a plugin check at Mozilla's page.
Folks in the Sea Monkey newsgroup think Mozilla is discriminating against SeaMonkey and Thunderbird...but Fx (two versions) and Pale Moon, which has a lot of Fx code, also cannot get a plugin check. So, I think there is something wrong with the page.