I just read through the Gen III gearbox pdf and it contained this comment:
"As with all gearboxes, a fine metallic “slush” or paste is not necessarily a problem."
I would strongly disagree that metal paste is acceptable in a gearbox after the break-in period. In fact if the gears are high quality, proper hardness, and isotropically finished, then no metal paste would be acceptable. The exception would be if there are slipping plates, rubbing surfaces or shift dogs in the box to generate the material.
I hope this gearbox contains a strong magnet to collect any metal particles so that they are removed from the flow path.
Disclaimer: This is just my opinion as I would not be comfortable with this condition. With careful & regular inspections and tracking of collected material, you may have a safe and adequate life of this gearbox. Just do your homework and pay close attention, don't just accept this on face value.