Factory bearings are of fine quality. Seems like a very rare event. I would let them use OEM for replacement.
It troubles me when dealers, mechanics and companies say
"Oh! Never heard of this before"
"Hmmm, this a rare problem"
Fact is, it's not rare. It's an ignored design fault and should not happen.
I had mine collapse last year. It started with an insignificant noise. I checked everything and saw chain needed adjusting.
Rode again and it was OK until a loud knocking that I thought was engine and got bike rescued to main dealer as it was under warranty
They rang me and told me that it had ruined the swing arm, the sprocket support assembly, sprockets and chain.
I got it repaired and as usual I found 5 others had similar problems of varying damage. And mileage a from 7000 to 20,000
I now change the bearings baring a at every tyre change regardless of wear.
Kawasaki shrugged their shoulders and just say it's not a warranty issue and do not accept its their problem. They tell me it should be checked at service intervals. I have my bike serviced every 6 months
I have ridden many different bikes even Moto X bikes and never heard of this
I never use high pressure washers
I was a police advanced rider
I have ridden motorcycles for 47 years and find this totally unacceptable but just insure the situation with bearings changed at every tyre change all the time I will have the bike