During the PGA Championship stroke play era (since 1958), 63 of the 65 eventual champions were ranked among the top 20 on the leaderboard at the end of Round 2. The exceptions are Collin Morikawa at TPC Harding Park in 2020 (T-25 after 36 holes) and Padraig Harrington at Oakland Hills in 2008 (T-26).
Here are the 36-hole rankings for all the major champions crowned at Oak Hill CC:
2013 PGA Championship, Jason Dufner, solo first after 36 holes
2003 PGA Championship, Shaun Micheel, tied for first after 36 holes
1989 U.S. Open, Curtis Strange, solo first after 36 holes
1980 PGA Championship, Jack Nicklaus, tied for second after 36 holes
1968 U.S. Open, Lee Trevino, solo second after 36 holes
1956 U.S. Open, Cary Middlecoff, tied for third after 36 holes
In short, every major champion crowned at Oak Hill CC was among the top three on the leaderboard at the end of Round 2.