If I want to achieve similar results to the guy in the article (who went from 33 to below 10 percent bodyfat in six months), do I necessarily have to, eventually, spend 10'ish hours in the gym every day?
No. Absolutely not. Only professional athletes would need to workout that long and they're not weightlifting or running that entire time (learning drills or practicing other skills usually).
Is it possible to get your body to below ten percent bodyfat training less than two hours a day?
Yes. Any effective training program can be done within 1 to 2 hours depending on what the program's goal is.
To lose body fat you need to be in a caloric deficit. Technically speaking, you don't even need to go to the gym to do that. Resistance/weight training helps you retain muscle while losing the fat so you'll have a more "toned" look than just being really skinny. Being in a calorie deficit, particularly a severe calorie deficit, will cause the body to lose both muscle and fat at the same time which is not ideal for health or physique.
Going from 33% to 10% in six months is pretty extreme. The article says he started at 245 lbs at 33% body fat which means he had 80.85 lbs of body fat and 164.15 lbs of lean mass. If he lost 65 lbs of only body fat and gained 5 lbs of muscle, he'd be at 185 lbs with about 9% body fat. Losing 65 lbs in six months means he lost 4 lbs a week.
My guess is (assuming the article is true and they're not lying) he lost a massive bulk of his weight when he was in the extreme caloric deficit of 1100 a day. The article states that he was only losing muscle at this time, but that's wrong. He was losing both muscle and fat at an extreme rate, but it states he went from 33% to 13% in three months so he was losing fat at a much, much faster rate. Then in the last three months he managed to regain what muscle he lost thanks to muscle memory and an extremely strict diet and maybe overshooting some thanks to being severly undertrained.
