Only long options are blocked from Monday. I think it is because of the high margin required later. For futures and short options, we pay high margin to take positions so its less risky than long options. Try reading their margin policy, you may understand better.
You may do intraday, but what if you or their RMS team cannot square off due to illiquidity? That is why they ask for easier operations. But it is still not compulsory, the form itself says voluntary. However, there is no disadvantage or threat by giving POA to them.