Logic would say that as long as it has the same certifications as the rebranded BMW oil then it should be fine.
I'm sure there's many high milage BMW owners that have not used BMW branded oil, I am not one of them so I can't say with first hand experience how it will fair in the long run. BMW rebranded oil and filters do certainly last for the long haul. Like I said there's good reason to buy BMW oil, if not for anything but the relationship with your dealer.
If you are concerned or think your oil was too dirty for 2k miles then get the oil analyzed next time, I've done it many times on various bikes, mostly when needing to push the interval recommendations on non-BMW bikes. Once or twice on my 07' BMW when it had 80,000 and then 110,000 miles. Came back with clean bill of health after 7000+ miles between changes. ( I usually follow normal 6k intervals or sooner but occasionally on long trips extra miles are unavoidable.)
The climate you ride in has a big impact on the oil life too, ride in dusty conditions regularly then you should change the oil and air filter more often.
Same for how hard you push the motor, if you never go through the entire RPM range then your oil will be good for longer, do track days or ride it like you stole it all the time and you should shorten your oil change intervals. Never bang on the throttle? Then don't worry about changing oil as often. Nothing with bikes is exactly the same since we all ride different in different places. The BMW 6000 mile interval is
generally. 7000+ miles for long highway miles with relatively low RPM's works fine, or if you are a guy who is constantly pinning the throttle and going to high RPM's you should change it earlier than 6000 miles if you care about the longevity of the motor.
Overall from my experience it's all the other small maintenance items: air filter, valve checks, spline greasing, final drive rubber boot being clean greased and sealed, final drive oil, outer front wheel bearing seals greasing, steering head bearing maintenance, rear paralever bearing maintenance, brake pads, fresh battery, etc. That makes the difference for many happy trouble free miles, not engine oil.
Most people would be better served to keep the rear end, front wheel bearings and air filter in tip top shape than changing oil more often than recommended. Again, it depends on the kind of riding you do. Ride in the rain all the time, you should grease things more often. Have a garage queen bike that never sees crappy weather? Then don't bother with as much "other" maintenance as often.
That's my unofficial 2¢.
