That sounds like more of a marketing line than a serious description of their testing program.Aero momentum website implies inflight testing is more important. Doesn't list ground test hours, so I haven't found any industry standard yet:
"From this point we have spent over a year testing both in the lab and more importantly in the real world."
But regardless, in flight testing may be "more important" in some ways but that doesn't mean you should skip or shortcut the "less important" ground testing. It's still essential to do the ground testing before flight if you're trying to minimize risk, which should be a major consideration.
I don't know of an industry standard either, but I'd want at least 100 trouble-free hours at full power run through a new design PSRU before I'd leave the ground with it. Raptor may have had 100+ hours on the ground before flight, but seems like only a couple hours tops at full power. I lost track of the redrive iterations so I have no idea how much time the current one has on it. Each time you modify it, you're starting over with zero time on the current design (although not zero time in terms of wear on any parts reused from the previous version...worst of both measures).
Raptor is spending a lot of time at 3,000 feet and lower 3-6 miles from the airport. That's at least approaching reckless without a much more thorough test/proving of the drivetrain on the ground. (Actually, I don't like that even in a proven airplane, but it's not uncommon so I must be an outlier in that regard.) The low altitude loitering isn't even the biggest concern in this regard, since takeoff power is the most stress the PSRU sees.
All that aside, I'm still thinking it's more likely to be an electrical issue rather than a PSRU failure that causes the first undeniable emergency. The PSRU may very well last many hours without catastrophic failure. But the non-redundant throttle-by-wire still comes to mind every time I think of Raptor, again most significant at takeoff. But the designer/builder seems blissfully unconcerned by it, even though it could be fixed easily and cheaply.