I don't think the simulator is designed to QA test the airplane. It's only for training pilots, and pilots are only trained on procedures that airlines deem worth training for. This is things like engine failures at inopportune moments, stall recovery, etc. The idea is not to simulate the outcome of strange circumstances, but to get pilots comfortable with procedures. So if there is some bug, it doesn't matter -- if you're training pilots to take off after v1* is called out and an engine fails at that exact moment, the instructor is not looking to see that "hey we applied the brakes and the airplane stopped OK with light rain and 3 knots of wind", they are looking to see that the pilot continues the takeoff anyway and doesn't try to stop on the runway. The pass condition is following procedure, not "well that's not the procedure but it looks like everyone lived anyway".

https://en.wikipedia.org/wiki/V_speeds#V1_definitions

The various data that feeds into training procedures comes from actually flying the real airplane.