Top Tactics Ratings Hard to Explain

How exactly are people getting tactics ratings as high as 8300 (which for some reason was then reset to 1200)?  I don't see how they can be solving very difficult 3000-rated positions almost instantaneously unless they're super-GMs practicing anonymously or something else is going on. 

They have probably memorized the puzzles

I opened a similar thread. Even strong GM here if you look at their tactics fail to solve some, while people who are not even NM have solved almost 100% of the puzzles in just a few seconds.

LittlePawn988 --  Sorry, I hadn't seen your thread.  I guess great minds think alike.

I think they use some kind of software or something. Cause I see some solving 6 move tactics in 1-2 secs. Don't know if it is even possible to make 6 moves so fast. Maybe, with premove? Certainly, will be nice to see the top tactic players solve tactics while recording themselves.