Even most professional endurance athletes rarely hit 28 hours per week of actual training time. That would be like a peak week in a training plan before tapering leading up to a race.

Even more contrary to GP's claim, the top American marathoners are only doing ~13 hour weeks of running before their races. It's public data on Strava.

If most people really wanted to I think they could. Split it into multiple blocks

If you are single and short commute, it is doable. People spend hours watching TV, looking at phone.

I don't think it's reasonable. That becomes basically the only thing to do outside of work. Highly unlikely at the very least.

Try only 4 hours a week of exercise. Most lean runners are only getting that amount of time running in and still eating high calories, because 4 hours of running is ~2,500 extra calories burned every single week.