In the place I train there are 2 girls few kgs heavier than me (I'm about 72kg). Our back squat number is approximately the same (around 110kg) but they can only snatch 60kg after training for more than 2 years while my recent snatch PB is 75kg. The same thing also happens with c&j. I certainly have far less experience than them and my technique is also worse.
That makes me wonder about what makes me to be able to snatch/c&j heavier weight. My theory is because I have greater upper body strength and better upper body structure to receive the weight like most males do. If it's correct then it's indeed important to directly train your upper body to be stronger. Unfortunately there's no way to change your frame. So it's now become clearer to me why I need to train my upper body. But will there be a limit to this where I can ditch upper body training and just squat, snatch, and clean and jerk like the bulgarians do? What do you think?