Reposted from Kotaku -
Could be a reference to Shepard’s death at start of ME2. Making the events of ME2 and 3 all take place in Purgatory. Everyone on Shepard’s suicide mission are individuals who are also dead, with their intro missions showcasing how that character actually died. Mordin never got a cure, Garrus died in his standoff, Thane died of his disease, Samara died against Morinth, Grunt was never ‘finished’, Jacob and Miranda died due to Wilson’s betrayal, Kasumi died alongside Keiji, Zaeed didn’t survive the bullet to the head, Jack never made it out of cryo, Liara, Joker, Chakwas, and Kaidan/Ashley didn’t survive the demise of the first Normandy (If the Systems Alliance never even looked for the Normandy wreckage/dog tags/Shepard corpse, why would the escape pods even get discovered?) and Tali died to Veetor’s paranoia/Atlas mechs. The loyalty missions were all attempts at the spirits finding closure. The Collectors were intended to get people to move on into their proper place in the afterlife, with Harbinger being an actual deity that just has poor communication skills.