Considering that KLM used to have a point based system, which was not very generous, I seriously doubt that there are many multi million mile accounts out there just from flying KLM, not from the comping of status and miles a couple of years ago certainly

IIRC flying AMS-SFO in C back then got you 5500 FD points, so even with the conversion rate of 1.83 to 1, one had to fly and save more than 500.000 FD points to mave a million miles after the conversion, IMO a very rare example of a real frequent flyer...