Shen Xia and Lilith already understood what was going on but did nothing to stop it in order to not tip off the General of their plan. They could have acted differently and stayed with the class, but that would not have made sense. By them acting as they did earlier to anger him until they only had to run laps, it allowed it to seem that they knew what the General was up to and wanted no part in it.
After class Shen Xia and Lilith were in the shower when a group of girls came waltzing over to them. "Shen Xia! Foreign girl!"
"Hmmm. It seems we will have issues getting out of her." Lilith frowned as she slowly turned off the water. The two had decided to shower together just in case this was to happen. It would have been worse if one of them were trapped behind a wall of girls being controlled by orcs.