There are certain situations where before the throw uke has a split second choice that he can do a roll or a high breakfall but he does the breakfall anyway. then there are some situations where nage is in full control and uke doesn't have a choice. In these situations, as the other poster said (probably because of your intensive ukemi training) the body goes on autopilot. You're OK after the fall, you meet the ground and sometimes, you don't know what had just happened. You just remember being flipped. You just let go and trust your experience will save you from injury.
I have found that when uke has the option of taking a fall or not, whether or not it is a roll or breakfall it means one of two things. Either the nage's techniques is wanting and or uke's attack wasn't very sincere.
The autopilot I understand. Most times when my sensei throws me, one second he is there the next I am on the ground and it isn't a painful experience at all.