DH situation

[DG]

NAIA 6.10-3 and 4 - The starting pitcher can be the DH (pitcher on defense, DH on offense) if the designation is noted on the lineup card prior to the game. The starting pitcher is the only pitcher in the game that that can assume such double role. Such player is allowed to remain as DH when replaced as pitcher, but may no longer play a defensive position.

NCAA 7-2B - If no DH is listed, the pitcher is automatically considered the DH on offense and the pitcher on defense.

So, how this works is if they start with a 9 man lineup, the pitcher can stay in the game as a hitter (DH) when he is replaced as the pitcher. The new pitcher does not bat. If you start with 10 man lineup this does not work because in this case the pitcher is not serving a dual role.