This isn't 100% true. The committee as a balance check adds up the top 4 seeds in each region based on where they fall on the s-curve. A perfectly balanced bracket for the 1 through 4 seeds add up to 34 for each region. Typically they will fall between 32 and 36. So as an example avoiding conference matchups and teams that met in the regular season along with a preference for putting teams in closer sites could lead to a region of something like 1, 5, 12, and 16. Its not particularly likely they would do that, but is certainly possible. People sometimes assume it will end up with regions of 1/8/9/16, 2/7/10/15, 3/6/11/14, and 4/5/12/13 based on the s-curve, but it almost never works out that way.