Because NC State
Was in the winner's bracket
Simple reasoning
Yes, that was the case in the first game, but both Kentucky and NC State were in the winner's bracket in that game. Last night's game, NC State was in the winner's bracket and UK was not, but UK was the home team. Not sure what will happen with tonight's game.
Apparently, the rules are that every team will get 1 home and 1 away game. If the two teams square off against one another more than once then they will do a coin toss to determine who is home and who is away and which dugouts. UK, it is determined, has an advantage with the covered bullpen, so if they are the away team they have to change dugouts so that they do not always get the covered bullpen advantage.