If you stick to interstates the gps software will generally guide you flawlessly. It's when you get on smaller highways that the trouble starts. But as others have pointed out, their gps works perfectly. It just enabled them to make some flat out stupid decisions.
I used my Street Atlas software to zoom way down on that area and there is a web of unpaved road around US 67. I think that people these days greatly overestimate their knowledge when it comes to doing things like this. They didn't see a 8 foot sign at the turn off on the gravel road saying:
DANGER! You could die if you take this road in bad weather.
So they assumed they could deal with it.
At Capitol Reef there is a network of unpaved roads leading to very scenic areas that 99 percent of the public never see. And I've been amazed to see people out there in their Prius or other tiny paved road only vehicles. Sometimes 30 or 40 miles off the nearest paved roads. We have a Ford F350 4WD. But those idiots are out there when at anytime a rain storm could render the roads impassible for an extended period. They certainly aren't ready to spend a night out there waiting for the road to dry out.