a few issues would like to point out. being sempai, assuming your skill is higher than the others, meaning you are in a teaching position when you are uke. the good way to train those lower than you in skills is to give them just enough resistance for them to work "through" the puzzle, but not to the point of completely frustrated which accomplished little other than raising frustration level and make you look like an ass. then there is resistance and there is stupidity. being stiff and turning your back on someone that can inflict harm on you from behind is stupid. something to think about, when someone is in your dead corner, what are your options? one of the options will get uke into the "face plant" situation, other options will not.

one of my sensei told me that you need to question everything, every assumption, every assertion, even past experiences, even from experts. asking why and figuring out the answers. don't just blindly copy things. you have to think about these stuffs.