Wait, how is the 1M NOT an "M" car???
To me, an M car is BMW sending over a 1/3/5/6/Z series to their special M factory.
The engineers at M take some parts laying around, mismatch here and there, throw a new engine in and BOOM!, an M car is born.
The Z4M is pretty much a parts bin car. M3 engine, CSL suspension, Z4 body.
The Z3M is even more so. M3 engine (both S52 and S54), E30 front, E36 rear, Z3 body.
The 1M is a parts bin car as well, but still a true M.
M is just the performance branch of BMW. If they can make an X6 go fast and handle great, then that makes the M name even better!
For an engineer to take an X5 or X6, and make it faster than 99.5% of the cars on the road today, and I mean CARS, not just SUV's, then that is amazing. I bet you an X6M could give a Vette a run for its money.