Puberty is a progress. and yes if you started to develop interests in actual masturbation at 8, then that was part of your puberty. As I said puberty is different for every kid. Sometimes the mind develops faster than the body. Starting puberty at 8 is not unheard of.

But maybe you also just all mirrored your surroundings even though you actually hadn't developed the sexual interest. That's also totally possible. I also watched porn once at that young age because we weren't allowed to. But it just weirded me out because I was too young to understand.