You're welcome
It's possible that the game forces the use of the Intel bypassing the gpu switch. I don't know how to check that. Maybe in log files ?
Additionally, you can try to raise the laptop, to allow air to pass under the machine. If you have a desk fan, try to refresh the laptop with (be careful not to block the computer evacuation air flow ). If you lower the temperature the internal fan will run less and you will get more battery time
