Roadghost nailed it - these articles don't take into consideration the number of miles traveled.
The young crowd with the sport bikes might travel 3000-5000 km in a good season, where as the older financially secure / retired guys might ride 20,000+.
It should be needless to say that the person riding four times the mileage (or possibly much, much more) is at a much higher risk of an accident, but that doesn't mean that they are somehow unsafe or unskilled.
Insurance rates speak for themselves.
I suspect the average older rider rides as few km as the average younger rider. There will, of course, be outliers.
Equating mileage to anything is not a good measure. It is much safer/easier to ride many kilometers on the highway or empty back roads then to ride them on city streets. I remember meeting a rider many years ago that rode 40000km a year. I was very impressed and figured he would be a very skilled rider. Turns out that pointing your motorcycle down an interstate and riding all day did not equate to skill....

Go figure....
I can hear the insurance rates speak.. they are saying "lies, damn lies then statistics..."