It doesn't try to prove that they will be equally good at running 10K, or have the same 'mental' benefits. That's a separate issue.
Think about all the people that are unable or unwilling to exercise like you do. Is it nonsense that they could significantly improve their health with short intense exercise? Who cares about fast and slow twitch fibres.
I took up BJJ (individual rather than team sport) as a way to fill my evenings, and to try to get back into martial arts. I've taken up a strength training (bodyweight) as a way to improve myself there.
The exercise isn't always fun, but it has a purpose beyond "run faster" or "lift more" (though those are fine goals as well, just insufficient motivators for me).
Congrats. I'm still a white belt and will probably remain one. They go to a gym up in Atlanta when they want to test and award belts, on a Saturday, and it almost always coincides with a soccer game. Priorities. :)
A major part of long distance running (10k+) is the mental aspect.
You are never, ever, going to get the mental endurance and discipline to run fast for distance by running for a short period of time, no matter how hard.
I think many people could easily train to do 5k and then 10k and get many benefits. Our very evolution came about from persistence hunting which means many people should have the genetics for endurance and far fewer for intensity (speed).
In the weight training community there's a thing everyone calls "newb gains". It's basically this study in played out in a weightroom. In a nutshell, it's that you don't need interesting training programs or massive amounts of gym time to get started. Just a few basic lifts a few times a week. Once you get a baseline, your gains level out and you have to start being smarter with your training. I'll bet a solid handshake that the same general pattern will apply here.
This study took out of shape people that didn't exercise and asked them to exercise. The program isn't so much important as is the fact that getting people doing anything strenuous ends up being beneficial.
Eventually their "gains" will level out and if they want to run a 10k in under 45 minutes, they're going to have do a lot more interesting training.
That's not a logical conclusion. The intense workout is to achieve/maintain normal fitness not to enable someone to run a good 10k.
If you can achieve moderate fitness with an intense workout then it seems much more likely to me that a person with such fitness will choose sports or other activities instead of remaining sedentary for the rest of the day.
[Citation needed]
You think a body builder could ever run a 10K at sub-6 mile pace or a sub-6 runner benchpress what a body builder could?
One minute all out may help athletes already in shape push to the next level. Like at the end of my long distance runs, I do a wind-sprint all out.
But regular people doing regular exercise benefit much more mentally from learning HOW to exercise for 45 minutes every day and increasing their metabolism.
If intensity training for a minute was all you needed, you could do sprints in the parking lot to train for a 45 minute 10K. Good luck with that.
Intensity training is good for fast-twitch muscle. Endurance training is good for slow-twitch. The two are not interchangeable.