We have found that when PerformanceTest is run on a remote machine via remote desktop and then the remote desktop window is closed or minimized while running the 2D tests, the 2D test scores can become extremely high.
The problem is that closing or minimizing the remote desktop window effectively removes the display from the remote machine, leaving the 2D tests with nowhere to render to. This leaves the 2D tests doing nothing, and doing it very fast, resulting in an extremely high score at the completion of the test.
Newer versions of PT have some checking to try and detect this issue however it isn't perfect and this issue can still arise in certain cases.