South Carolina athletic director Ethan Hyman was on the NCAA baseball tournament selection committee this year, and this account of the process is pretty interesting. Especially this bit:
Kentucky was the surprise omission for a host site while Miami slid into one of the 16 slots. Then, according to Hyman, seven of the top eight national seeds became clear, and the discussion came down to the eighth seed.
USC fell into that "gray area" along with N.C. State, Purdue and Stanford. At that point, Hyman was permitted to state his case for USC and occasionally texted Andrew Kitick, USC’s sports information director for baseball, seeking further statistical information.
What's confusing is the fact that NC State was in the mix for the last national seed but somehow ended up the lowest ranked host school based on its projected Super Regional matchup against No. 1 overall seed Florida. (Or, at any rate, ended up with the worst Super Regional draw among regional hosts.) This snippet suggests that the committee regarded State as the ninth, 10th, or 11th overall seed in the tournament, which would seem to mean pairings with the eighth, seventh, or sixth overall seed in the Super Regionals.
Maybe it just doesn't work like the NCAA basketball tournament; structural differences being what they are, maybe they aren't so exhaustive, S-curve style, in layering the tournament. With no national seeding beyond one through eight, it's tough to say.