yes you get items if you are far from the chest. There is only 1 chest to click on so if someone else gets to it before you, you dont have to click it, but the items are randomly distributed. The loot works similar to defeating an enemy if you are far away you dont see who gets the item unless its you.

Also dark matter is a reward for people for low scores, I dont think I have ever got from the chest DM from high end scores