Yes, they amass thousands upon thousands of games at a very young age. I did the same programming my C64 in 8th-10th grades. The hours just fly by, doing what you love.
One other factor is that 3500-level chess engines are freely available for anyone with the net to analyze every situation, every move.
And then there are the streamers like Hikaru who teach chess so brilliantly. He is a true one-off, to be that top-level and able to live-comment his own blitz games. It is an underappreciated and completely unique talent, and enlightening for the chess afficianado.