There's also tangential evidence that Pathways Into Darkness, Marathon, Halo, and Destiny all exist in the same universe.
And with this recent 30th anniversary event, it also seems like they kind of think of all of their various older IPs to be in a multiverse of some sort.
(And Pathways into Darkness was also an FPS, just like those three Marathon games. Bungie has been doing FPSes for a long time, 100% agree with you.)