I have done the tour - there is definitely oil in the engine - they said they don't fire the engine with fuel for a few reasons, one is the cost - the save a zillion dollars if they don't have to burn a few ounces of fuel in a million less engines, no emissions issues to deal with and no danger of having to have fuel etc in the area.
M engines are still wet fired though.
2008 E93 335i, MHD, HPF IC, Injen Intake, AR DPs, Alpina TCU Flash
2016 X5 M-sport 35i JB Stage 1
2013 Mercedes C63 AMG, ROW airboxes, power pipe, Eurocharged V6 Flame tune 540 HP