Always tough to trust second hand or partial info. This is where speculation gets the worst of us.
Is there any comprehensive data logging with any of these failures?
Are there any images of the main bearings?
Do the rods look over heated or warped from excessive heat, or just damaged?
When there IS oil starvation, there are heat tells in the bearings, rod, main, and sometimes even the crank will warp some. Since the mains are fed before the rods and loose oil flow first, starvation almost always leaves a tell on the main bearings. With ONLY rod bearings damaged and no data or heat signatures anywhere, you really need to tear down the entire engine and have some one that knows what they are looking for review to find the failure mode. With solely rod bearing failure, I would more likely suspect rod knock.
Mahle has a nice
bearing failure guide if anyone wants to dork out on this stuff.