At this stage the MMs are not in any way, shape, or form, required to do anything with an order. They can simply throw in in the garbage if they dont feel like making the effort to look at this.
This answers 2 theories:
1) Why people have had orders in and not got filled*; 2) Why the suspicion of the trades that do go through may be orchestraded.
*Also note that most orders on grey sheets must be matched exactly in order for a trade to be executed.