Has your partner ever let go of all support while you were at 1/3 of a breakfall cycle? Or even worse pulled all the weight down while you were "writing" a lovely circle in the air?
I have witnessed and experienced both (along with a lot more colorful situations) and the end result was always injury, no matter how advanced the uke was.
So... i only take breakfalls from people i know and trust.
I have experienced both, and while they were not comfortable, I was not injured.
My sensei's first priority when I graded to shodan was ensuring that I would be safe, no matter where I trained. This was particularly important to him as he knew I was moving away soon. He wasn't too concerned about technique, just that I could fall safely in the sort of potentially dangerous situation you described. I think you guys need to work on your ukemi a bit.