for the Regionals bracket. Does this mean anything else other than one team goes through with 3-0 or 2-1 (head-to-head tiebreaker), or there's more to it?

Tomorrow, a 2-1 team will face a 2-0 team in the first game. If the 2-0 team wins, they advance. If the 2-1 team wins, then they play again and the winner of that game advances. Every team has to lose twice before being eliminated.

that premise is not totally wrong. It's just if you are 2-1 against a single team you had to win 4.

Are you confusing the pool play of the ACC tournament with the regional format?

He's just making it overly complicated.

You can also advance by going 1-0 against two teams and 1-1 against one team.