As far as I know, the original reason for the 5 & 6 seeds crossover wasn't
because of any real or perceived lack of quality in the east, but because
of a desire to increase interregional play.  Usually, six teams from each
region are selected, but four of those twelve teams are sent to the other
region.  Admittedly, it's probably a little late to start interregional
competition during the finals, and we end up with situations where four teams
from one region make up the final four, but the intent was not to limit the
number of Eastern teams in the NCAA tournament, at least as far as I know.
 
Kristen Robinson
MSU '93, UK '95 (I hope)