This makes perfect sense.
You have a 2.3GHz cpu, now TURBO brings it up to 3.3, but only when you load a single core up(and then it can idle out the other cores).
If your game used 2 more, it can not go all the way. Chances are you get times with some mid speeds, but turbo is made to allow single threaded(even 2 and 3 threaded) programs to run faster. It is somewhat hard to run 3-4 fully loaded threads within a 45 watt power envelope.
This can vary as said with temperatures,load(power consumption) and even the way the laptop makers sets up the system.
You would try to maximum performance power option to see if it lets it go higher.