If someone has only ever twisted their Ford V10 to 3500rpm max, that’s one slow ride. The one in my E450 cutaway in normal driving will generally upshift at 4k. Any hill will drop it from 5th to 4th, with an rpm jump from 2500 to 4000. It has had numerous foot to the floor moves where the 5R110 will shift at 5000. The Coyote in my F150 rips upshifts at 5900. In Mustangs, the same motor with different cams is redlined at 7000.
But back to the Godzilla, it was my understanding too the HD and light duty versions make the same power, just on a different ratings scale for each. And I’ll bet the transmissions WOT shift at the same 5500 rpm or higher in either too.