Hate to be that guy (just kidding. I love it.), but this is one of those pieces of conventional wisdom that is not backed up at all by the data. From
“It’s Hard To Beat A Team Three Times” | COACH BOB WALSH:
"According to STATS LLC., there have been 981 similar matchups across Division I college basketball over the past 10 seasons. The teams entering the third game 2-0 are a combined 710-271 (.724 winning percentage) in the third meeting.
So over a 10-year period in college basketball including almost 1,000 games, the team that won the first 2 games won the third meeting 72.4% of the time. So it clearly doesn’t follow that it is hard to beat a team 3 times. In fact, it’s actually kind of easy."