That article was published exactly one year after the introduction, at the time about a third of all delivered aircraft to date were delivered, theres some lag from delivery to first revenue flight, so its plausible that less than 100 had been in revenue service.

So, with all the lag in getting the aircraft into service, its plausible that in the next 10 months the type could rack up 500,000 flights, since thats just a little more than 4 flights a day per aircraft on average.

Thanks. It still seems very surprising to me, but I agree it's plausible.

I suppose someone with full access to data from e.g. FlightAware could try to see how many total logged flights there were.