If it was locked in and he "fell back" you could have seriously damaged his neck.
A locked in guillotine has you "leaning back" and press in and up with your forearm against his neck/throat.
Maybe I misread your post, but for him the make you fall forward, with him in a guillotine, and him NOT getting hurt, seems like the guillotine wasn't "locked".

Actually, that is a very effective way to escape the standing guillotine. Izza was correct in what he saw in Renzo’s book. The first thing is to simultaneously:
A. Throw the arm opposite of the side your head is trapped over your opponents shoulder so the crook of your elbow joint rests on his shoulder.
B. With the other hand you grab their wrist by your throat and pull down to also help relieve pressure.
They can lean back and fully pick you up off the ground and all the pressure is off of you. Let them lean back and hold you all they want… eventually they will get tired and your feet will touch the ground. Once this happens you have several options. One of which is the throw Izza spoke of. With your one hand still relieving pressure on your opponent’s wrist, you place the other hand on their hip. Step through with one foot and just plant your ass on the ground by your heels and roll back using your legs to help the throw as well. They will either plant their face on the ground (this would friggen’ hurt them bad) or tuck their head and roll over. Most trained people will roll over in which case you are side mounted while possibly still in a guillotine (not likely though). Escaping from here if still in a guillotine is easy as their leverage is gone. If they lose the guillotine you now have side mount. I am generally 20 to 60+ lbs lighter than my opponents and I can make this work very efficiently. It’s all leverage when done properly. It doesn’t hurt your neck at all. There are more fine points to refining this but they are tough to describe via the internet. Using the hand on the hip during the throw is one, which can make a big difference if not used properly.