From the videos it looks like you ride pretty far forward on the seat. Partly because I have a small frame, I tend to ride up on the front of the seat. But people tell me that riding forward on the seat makes it difficult for sufficient weight to be put on the rear wheel, so it isn't good. I do tend to ride farther forward. It is not something that I do consciously, it just happened naturally.
Some people ride forward, some farther back.
I believe that almost everyone has their own style, just like there are lots of different kinds of machine settings. I don't believe that you can say conclusively that forward riding is not good. I am the only Japanese rider with no real experience in 2-stroke riding, so I feel that I have to work even harder than the others. When I win I feel really relieved. That is something I spent a lot of time to master.