Yep sort of figured it was iRacing shared memory giving wrong info, seems like its a common problem with many of the sims not allways providing correct data, ive been having lots of issues with assetto corsa and its shared memory when adding it to crewchief.
Speed is given by the games, but almost always as a relative speed of the car. You will notice the speed matches for instance the speedometer of any overlay on any game. It's the in-car speedos that apparently don't show us the same values