I don't think so. My clown girl refused F/T no matter what. Weighing a whopping 110g I didn't want to hold out longer than the month and half she went without eating. Offered live and she ate. Now she won't even eat live. So yes there are some snakes that won't switch. Heck this snake won't even eat at all right now. :/
From what others have said the squeezing releases endorphins which lessens the pain. The rodents die rather quickly.