The AI certainly do pitstops and pitstops are animated too.
The AI will pit for fuel and tyres, they will also pit to repair damage or to change tyres if it starts to rain. However, I'm not aware that you can give the AI pitstop strategies. GTR2 is based around the 2003/4 FIA GT championship where the races are 3 hours long and you have to pit twice because otherwise you'd run out of fuel. Fuel weight doesn't have the impact on laptimes for a GT car that it does for an F1 car so there isn't the same benefit to running less fuel and more pistops. A two-stop strategy is always the best.