Utter bollox , your fluid had absorbed water and needed changing.
Oem fluid does NOT easily boil , i have used it on track and not boiled it with standard genuine renault fluid changed by the dealer the day before.
If you can drive that hard on the road your not very bright. As it would be lunacy
A) You're wrong.
B) You're wrong.
C) You're wrong.
The E46 had extremely poor brakes when they come off the line let alone 5-6-7-8 years on. A quick browse of the owners club would also show I wasn't the only owner that thought this as a lot now have larger caliper upgrades or at least more focused pad compound.
The M3 fluid is also PRONE to overheating. Again a little time searching would show I'm not on my own there either...
August last year we managed just over 5 laps before we boiled the OEM fluid, yes the car gets 'punished' more on track however OEM fluid simply isn't the best for that type of use.
I'm not arguing OEM fluid has it's uses, I'm also not arguing there is better than ATE however I would state that ATE is much better than OEM with the only drawback I found is like you have already said it needs replacing a lot sooner. For for £15 and a hours labour the increase efficiency is well worth it.
A lot of your posts at the moment seem to be on very argumentative so I'll leave it there for now we each have different opinions however trying to argue that OEM is as good as aftermarket fluids is pretty pointless.