2011 is far from the only time the Mosconi Cup has used races other than to 5:
1994-1997 -- best 2 out of 3 races to 3, but you had to win by 2 games, and that was ended (capped) when someone got to 5. So the winning scores for the races were 3-0, 3-1, 4-2, 5-3, or 5-4. And to make it even a bit more odd, in 1995 the last match was just one race, and in 1996 the last 4 matches were just one race (time problems perhaps).
1998 -- races to 7
2006 -- races to 5 in last-day singles; 6 in teams, trebles, and doubles; and 7 in singles prior to the last day
2007, 2009, 2011, and 2013 -- races to 6
2010 -- races to 6 on Days 1, 2, and 4; races to 5 on Day 3
the other 21 Cups (1999-2005, 2008, 2012, and 2014-2025) -- races to 5