nOt all western saddle put you in that position. My saddle allows me to have my legs nearly straight down. In fact, my legs are more straight down than in a hunt seat saddle. And, I sit more directly on my seatbones and carry LESS weight on my thighs when riding western. I like both ways of riding but find that riding western I ride more from pure balance in the seatbone, no gripping.
English, I tend to kind of carry more weigh on the whole pelvis and the thighs, and kind of wrap aroudn the horse with the leg and ride with more grip and strenght, thus can deal with more sudden changes, like dodging puddles or leaping small logs on the trail.