It's not really true.
Pop is 17-16 since 2014s Duncan coached Championship.
That's a nifty, what .501
Yeah, 17-16

3-4 vs Clippers in 2015
4-0 vs Grizzlies in 2016
2-4 vs Thunder in 2016 (game 2 remains a huge but punch)
4-2 vs Grizzlies in 2017
4-2 vs Rockets in 2017 (2-0 without Kawhi to finish games)
0-4 vs Warriors in 2017 (+21 with Kawhi)

Amazing that it's just one game over .500 over that stretch.