That's 100% driver error. Not a design error. You can't idiot proof everything for everyone. If the guest driver would have come to a complete stop it wouldn't have mattered what gear they shifted into. It's bad practice not to come to a complete stop before shifting from reverse into any gear, or into P. Even on a manual trans.
Not really. It's a combination of user error, which should be prevented by a better design. So I'm not saying the driver didn't make a mistake, I'm saying the driver did something wrong, out of habit (which is his fault), but the bad design allowed him to do this.
Think of it. We've had decades of user interaction with knobs on the HVAC and radio. Now all of a sudden they put a third knob there in the exact same location which does something completely different, and it's a very critical piece of UI. If you turn fan down instead of radio, who cares. If you shift to park instead of drive, it can be pretty bad. So they're introducing a UI element which is far too similar to other controls, but is dangerous to get wrong.
Second thing is; the knob does have a safety mechanism in it (so they even understood/predicted the issue to some degree and attempted to mitigate it) which prevents changing gears at high speeds. OK, but it didn't work in my case. The whole truck rocked and there was a loud clunk. Whatever they're doing, it's not sensitive enough
Better designs are out there, including the standard gear shift lever. Absolutely nothing wrong with it, especially in trucks where there is room for more bulky controls. GM's shifter is electronic as well, so it can be done even without mechanical linkage.
There are also other designs, like GM's shifter in the new tahoes (push buttons).
FCA has had other issues with shifters, like the one in the 2014 Grand Cherokee which ended up killing a famous actor. Same thing there, people complain on forums about the poor design and then other guys say "it works great, problem is the user".
Fine, maybe the user is a complete idiot, but the fact that they later improved the shifter so said idiots wouldn't kill themselves proves that they had room on the table for large improvements to be made. That's the case here too, it needs improvement big time.