This is what Car and Driver thought of the 4.6 at the time of introduction:
https://www.caranddriver.com/reviews...ake-road-test/
Was it enough better than the ML55 and more importantly the 4.4 to deserve an M badge? If judged only by the 4.4 0-60 times, stopping distance and skid pad I would say yes. That is certainly 20 years later of Monday morning quarterbacking. The fact is BMW didn't choose to do so. Based on the logical considerations of a 2002 decision I think they made the right decision whether it meant the appropriate standards or not.