Just found this out and wanted to share. Loaded up a random Bugs of the System normal. Sent me to the future one. Cleared it easy enough, but then I saw the door wasn't completely barred shut like I thought it was. Sure enough, if you jump up to the hole? You can see inside the tomb. Good show Bungie. Now let us enjoy our missions whenever we want so more titans can kneel at the original badass who punched things.