I think you are mixing futures market with stock options. Stock options are live until 4PM (EST) and some index options actually traded until 4:15PM (EST).
What I am wondering is if market makers look at the both call and put options and see which side would be cheaper to cover and move the market that way.
For instance, if there were a lot of put options that were in the money vs. call options, as it may have been today, that could motivate them to move the market up and let many put options become worthless.
Don't know for sure, but it would seem there is a financial value to swing the market one way or another.