This is not actually true, though to read the UConn media guide you might get that impression as they are inaccurate on first team AA status for Bria Hartley:
As a sophomore in 2011-2 Bria earned WBCA AA status, she had an ankle injury that hampered her junior season and did not get voted an AA but Dolson her junior year and KML her sophomore year did, so at the start of the 2013 season Bria, Stef, and KML were all already qualified for the HOH wall as first team AA. If you want to qualify the statement as returning three members of the previous years WBCA team - than I am sure it is unique. But UConn has had 3 returning AAs in a season before. (By the end of that year they had four playing on the team as Stewart earned her first that year.)