I have seen the Sikorsky S-92 gear box test report for the run-dry test conducted in 2002 and, to my recollection, the gear box suffered a catastrophic internal failure very shortly after the 10 minute point. I am not aware of any subsequent S-92 run-dry test except for the one conducted in 2003 using a cooler bypass feature (not run-dry) which culminated in the FAA decision to grant certification under the "extremely remote" provision.
I have heard many stories of short run-dry flights on pressurized transmissions (I have one myself) but the time from first indication of an oil loss to a successful landing or ditching has been quite brief in all cases that I'm aware of.
If a helicopter MGB is certified by a Technical Airworthiness Authority to run-dry for any length of time, it is not merely an "OEM claim"; it has actually passed the test under stringent conditions with follow-on strip down inspections witnessed by the TAA.
The EH101 was the first helicopter to pass the onerous FAA/JAA run-dry test (in 1993). A production version of the EH101's Advanced Technology Transmission was flown on a rig with loads simulating a max gross weight aircraft for a full thirty minutes after all oil (except residual oil that remained in the bearings) had drained from the box plus an additional 2 minutes of flight for approach and landing.
In 2013, the AW189 passed an identical run-dry test but demonstrated 50 minutes plus 2 minutes for approach and landing. In both cases, the strip inspections revealed some heat damage but nothing that might lead to a catastrophic internal failure.