This has always been rule for anyone who came to the UK on a spouse visa, though what has changed recently is that spouse visas are now 27 months when they only use to be 24 months.
From
http://www.bia.homeoffice.gov.uk/ukr...ionformset(m)/
"Please do not send us your application more than 28 days before the end of your two-year qualifying period."
It's only anyone who came here on a fiancee and now has FLR who cannot apply for ILR until 28 days before their visa expires because their visa and their 2 year qualifying period are between the same dates.