These results are based on one year though. I'd be interested to see what they've been for the past several years.
Also, putting the YES next to Mahomes seems a bit disingenuous. Alex Smith started all their games except for the last one where they rested starters.
2016 playoff QBs:
-AFC: Brady, Roethlisberger, Smith, Carr* (hurt, but got them to 12-3), Osweiler, Tannehill
-NFC: Ryan, Rodgers, Wilson, Prescott, Stafford, Manning
Only two of those QBs (Carr and Prescott) were on rookie contracts. The Raiders were one and done (Cook started) and the Cowboys were also one and done despite a #1 seed.
2015 playoff QBs:
-AFC: Brady, Roethlisberger, Dalton/McCarron (Dalton got them to 10-2), Manning, Smith, Hoyer
-NFC: Palmer, Newton, Wilson, Bridgewater, Cousins, Rodgers
Only two of those QBs (Bridgewater and Cousins) were on rookie contracts. Both were one and done.
2014 playoff QBs:
-AFC: Brady, Manning, Flacco, Roethlisberger, Luck, Dalton
-NFC: Wilson, Rodgers, Newton, Stafford, Romo, Palmer/Stanton/Lindley (Palmer got them to 9-1)
Rookie QBs: Wilson, Newton, and Luck. Wilson makes and loses SB, Newton blown out in divisional round, Luck blown out in championship.
I honestly think this year was an outlier. Interesting to look into though.