This issue dates back to rFactor (1). Despite the checkered flag coming out, if you start a new lap after the timer hit 0 and can complete it before the session moves over (due to length of lap or someone on a valid lap causing delay), the new time will count so if you're faster you can move up the grid. I tested it yesterday while online showing someone the exploit with Quebec Medium (Long too I think) where you go right onto backstraight after T1, and despite starting the lap after the checkered flag I got a new faster time for my pole position.