Why do people oppose long revision sessions?

Seven hours a day is monumentally better than 1–2 hours of studying. People just use studies that say otherwise as a coping mechanism to continue scrolling through useless social media. Sure, it might be enough to learn the syllabus and get you A–A*s if done consistently, but you won’t achieve nearly as much as with seven hours of consistent study.

People aren't suggesting (at I haven't seen), that you should only do 1-2 hours a day. I think they are suggesting taking breaks, otherwise you will have brain fatigue.
Doing 1 hour of work, then a 20 minute break and then another hour of work does not reduce your amount of work that much.
Though, I don't typically follow this. I worked for about 2 hours at A Levels and then took a break, which I found effective.
It's also about what works best for you. If it is better for you to work for 2-3 hours and then take a longer break, so that is fine. I also think that if you work better with lots of breaks, the you also need to practice being able to sit a full exam.