I would suggest that correlation, causation etc & vice-versa aren't related here.
I've held a street licence since 18 and have spent a fair share of time both on and offroad. I've taken several offroad courses taught by world class riders and now spend most of my time in the woods. I've also taught offroad skills improvement courses to numerous riders. I've raced some at a mid level, but really prefer recreational trail riding.
Here is some of what I've learned over the years;
It takes a short time to become reasonably proficient in a very basic way to handle a bike on the street(riding sense not included). It takes about 5 years(500-1000hrs) to become well skilled offroad.
The only riding skills that transfer from pavement to offroad are the most basic riding operations itself; clutch/brake/shifting. That's it. Even then, the braking has to be relearned.
HOWEVER, all of the skills acquired offroad(and there are a lot of them) do transfer directly to pavement riding, massively improving the riders skills in handling a bike on pavement. This cannot be overstated. It's no accident that world class motorcycle road racers spend their practice time riding dirtbikes, trials bikes, ice racing and flattrack bikes.
It's the same reason why so many dirt track & rally car drivers make great pavement racers- they learn transferable skills you just can't learn any other way.
It's easier to teach girls and women to ride offroad than it is to teach guys.
You can lose 5lbs and burn as much as 3000 calories in one National enduro.
My worst injuries all happened in crashes at speeds of less than 5mph.
Graham Jarvis probably isn't human.
One needs to learn to be both defensive and offensive when riding on the street. Some of that can be taught, some is instinctual, the rest is luck and experience(if you make it that far)
All the skill, sense and experience in the world can't protect you from really determined idiots in cars/trucks etc. Often, it's just luck.
Stupid or overconfident riders on the street are their own worst enemies.
I suggest to all noob riders that I meet, to learn to ride offroad first. It's much better for them.
Not every dirt only person will be asphalt stupid. It's all in their mental approach to street riding, or driving. They also have bike handling skills pavement-only guys can only dream of.
Without knowing all the details, I can suggest with good odds that your young Suzuki friend's death very likely had nothing to do with bike handling skills, asphalt or not- he had them in spades. The asphalt wouldn't be a factor. It was something else that caused the death.
I rarely ride on the road anymore, as cagers these days are too pre-occupied with non-driving related things. I also get bored easily on the street, which is not a good thing, so I generally avoid riding it where possible. My road riding these days generally consists of a short hop down a back road between trails. If I crash offroad, it's my fault 99.99% of the time- even though I may try and blame it on the tree I just hit, or (insert obstacle here). lol.
On the road, the %ages are reversed.