Not sure I follow this for a meat cooked to that's high of a temp. Sure I can see if your eating the meat at 145 or near that...
I'm watching for the "official" answer, but here's my understanding. The bacteria that makes food get us sick create toxic spores within the meat. I'm not 100% sure where that actual time frame came from though. I'm sure there's a reason.
So by cooking to these high temps, you are in deed killing off the bacteria, but you can't remove those toxic spores that were created with heat. If too many toxins are created (longer than 4 hours?), you chance getting sick off of the end product.