I've done an oil change today at 11k miles where the oil had a hint of sparkle. I'm sure, however, that the first few oil changes contained small sparkly particles.
The difference in "sparkle" is the difference between gears in a new gearbox knocking off relatively larger pieces (though still pretty small) from each other as they settle into mutual harmony, and much smaller pieces worn off by grinding two pieces of metal together with tiny particles in progressively more dirty oil, plus the detritus of inter-metal (steel and aluminium) corrosion.
When I was a student, I trashed my Porsche racing in the storm gutters beside a section of the road in what was then still Southern Rhodesia. I had to be in class Monday morning at 0800 hours over a thousand miles away, because I'd tangled with the Comtesse de Reville over some curious lacunae in her textbook (in a book on markets, she didn't even mention Karl Marx) and she had announced I'd better not cut any classes to play polo or race cars or speedboats or sailing yachts or any other sporting "frivolity" or she'd get me rusticated (sent down, expelled). At an auction for used car salesmen, I bought the only car I had enough cash for, an ex-highway police pursuit Jaguar Mk II with 250,000 miles on the clock. I paid £50. It saw me appear for class Monday morning at 0755 in Stellenbosch. I actually set some records with and raced this car, and then used it as a tow car for my racing cars. When I next passed through Rhodesia, I told the police commissioner, seated across from me at dinner in Government House, about this marvellous Jaguar. The next day he took me to see the wizard of longevity, the chief mechanic of the colony's police force. This old-time time-served master craftsman showed me his secret: they never switched off that car's engine. It was operated by three shifts around the clock, 24/7/365. Every 3000 miles they changed the oil with the engine idling, pouring in new oil at the top while draining old oil from the bottom, until the oil running out came out clean. I don't quite know how you would do the same with a Rohloff without spraying oil everywhere, but the 3000 mile oil service cycle for that miraculous Jaguar (and all their other pursuit cars) sounds very much like the Rohloff suggestion of an oil change at 3000 miles -- a proven, validated precautionary measure.