Alright, bear with me here - I'm about to get really fucking schizo.
As of the conclusion of Ace Combat 8, it's been EXPLICITLY confirmed that Strangereal has a genuine afterlife that all pilots go to when they die. During the epilogue cutscene of riding backseater in a Rhino with Kate while flying recon over Sotoa, the desert landscape outside vanishes into a full-blown vision of a pristine prairie, the souls of the dead flying free overhead as white birds, two of which are Cope and Tewy as their souls finally reunite. And when the vision ends, the dogtag held in Rex's hand has fucking vanished completely, only to somehow reappear a good few thousand feet outside the cockpit on the ground below.
Over the course of the campaign, there are a few other moments where, despite the game being very strictly limited to Ray's personal perspective, we get quick glimpses of things that he should not be able to see - mostly it's just minor, very quick external perspectives like D.D.'s social media antics, Pike alone at a desk, Tasha after the funeral, etc., but a few are almost deliberately odd in how they're framed. After the battle with Tewy, for example, the PoV flashes across the various landscapes of Usea before somehow diving into D.D.'s phone camera, then flipping out out of it to an omniscient view of the scene in the Endurance's briefing room, the swooshing "camera" movement feeling almost uncanny with how deliberately grounded the shots otherwise are. And in the prior duel, when Tewy herself is shot down and flung out of her plane's cockpit in slow-motion, she makes a whole statement to Ray before the craft explodes and cuts her off as time snaps back to regular speed. And yet, right in the next misison, it's made a major plot point that EVERYONE from the Jokers to Dealer all heard her exact words - when not only was she no longer connected to her plane's radio, but also speaking within a bullet time sequence, because the real-time sequence of events didn't last long enough for her to speak her message. AND THEY ALL HEARD HER.
So, ghosts are real, the afterlife is real, and not only can Rex perceive them, not only can he perceive other things that should be outside the scope of his awareness, but he can also somehow let others perceive them as well. And just exactly why can he do all this when nobody else can?
It's because Rex is you.
I'm not talking about Rex being self-insert for the whole power fantasy - Rex is literally a manifested avatar of the player themselves within the fictional reality of Strangereal. Kono himself explicitly stated as such in the Famitsu interview:
"With some exceptions, for thirty years, I basically followed the first person, 'I (myself) have been through the experience of an ace pilot in the world over there.' The player is yourself, so you don’t have any extra memories of the game, and you don’t suddenly meet your separated father. Go to the Strangereal beyond the monitor as yourself and (set) out to be active as an ace pilot."
We all naturally assumed he was just talking about the player being a blank slate for maximum player immersion, but I'm starting to suspect that he was being literal. Just like Mihaly was a meta-commentary on veteran players, what if Rex is a reflection of players being uniquely able to understand and connect to the vanquished and fallen pilots beyond what someone in-universe could?
Getting back to the Watsonian element, in the aforementioned epilogue cutscene Cope mentions how the souls of the dead are unbound from physical space, yet they surround it completely - so whatever the afterlife is, it's something adjacent and parallel to the material reality of Strangereal. Baxter and Kate both briefly see Cope when they're on the brink of death, so passing through or near that boundary between life and whatever follows seems to grant the living an awareness of that parallel reality that they'd otherwise lack.
Now, if Rex's sentient awareness exists outside of Strangereal, then it's pretty much in a perpetual state of transit across that boundary with every single input/output- if Baxter and Kate are radios that start to pick up a weak signal from another room when they're in the doorway, Rex is a pair of radio comms with one half inside the building and the other in a completely different building, picking up everything just because the distances of the transmission and reception involved make it incredibly sensitive to "background noise" that would otherwise be imperceptible.
We're able to perceive all that spooky shit - the voices of the dead, the last words of the dying - the originates from beyond the material plane because we originate from beyond that material plane as well, albeit even further out. This is why, when Tewy overrides the safeties on her proto-ENSI control system and ramps it up to 145% or some shit, she starts to read your exact control inputs as you do them; she's pretty much dying from the neurological strain, her Copro gradually uploading her consciousness into the machine to evacuate it from her failing physical shell, her vision going blind because she isn't inside it anymore, and as she passes across that gateway between the material and immaterial, just like Baxter and Kate could at the brink of death, she can see Rex, see us perfectly.
And after all the jokes and complaints about Project Aces ripping off Project Wingman, we get one last nod, and the greatest of them all:
We are the king of the dead, and the keeper of the high garden they all return to.
