If he hadn't included the parenthetical, I'd have read it as sarcastic too. But he did, so I was unsure.HRB hedged well and was tongue-in-cheek, so this is not a dunk.....but it's very very funny that the first two examples were two of the most successful coaches in history, and are both still active.
One can certainly debate whether Popovich was a "Successful executive" before he came down onto the court, though there's no such debate with Riley.
Bobby Cox was a manager for the Braves from 78-81, then their GM from 86-90, then back to Manager from 1990-2010. Given the talent he'd brought aboard as GM (Smoltz, Glavine, Chipper, David Justice, etc), I think he meets the test too.
Jack Adams was GM-Coach of the Red Wings for two decades, successful in both, but the coaching didn't follow the executive role. Similar for Paul Brown, who coached-GM'd the Bengals after (very successfully, of course) coach-GM'ing the Browns for two decades. But he didn't leave the sidelines until he was 8 years into coaching the Bengals, in 1975 (and then GM'd another 16 years).
Maybe there aren't a ton of great examples after all, even if we can snarkily come up with 2 in the NBA pretty quickly.