No, there is some confusion here. These are two different things. The margin for options and the margin for futures. If you are long a put, you pay for the premium in full. If you "choose" to exercise that put and he short the future upon expiration then you now have the margin of holding a future position. It's no longer an option position. It's important to keep the two separate, they are not the same thing. What made matters worse is he kept talking about the put not requiring any margin. As for expiration day, I'm not sure what he is referring to. You, the trader has to take ownership of any risk you have on expiration day. Almost every broker I know of sends out notices making sure you are aware that you have in the money options that could be exercised against you or given to you.
I do not support delivery/optionexercise too. as I told you, we are human being. sometimes we may have some mistakes and let that happen. totally understable.