I agree, there is a difference between them and it looks like your guys have bugger all core stability if thats the case (not that I'll say it to their face) but even with pussy weights, doing deadlifts wrong will bugger your back up, just informing those that may not be aware that it can be dangerous. I had a mate at uni that threw his back out deadlifting like 30kg Doing it faster will only make it worse too, so although the weight is low, the speed of doing it and doing it incorrectly could injure you.
This reminds me I need to get back into some form of exercise, become a right unfit bugger recently!