Well, it isn’t about whether they knew about it; of course they did. It’s likely they either made the theme or had to authorize use of the art assets for it.
The point is that this is almost certainly part of the publishing agreement with Sony, which has specific and presumably rigid terms based on what I’ve read and heard from folks - and there’s a disconnect here - technically, we in fact, did not pre-order the game with Sony, because you didn’t pre-purchase it through Sony’s own store and directly contract with them, you paid Airship directly via the KS campaign and they roundabout provided you the key for your game.
It sounds silly, but I mean, it is actually different. Super common thing with Sony; they constantly do this with themes, certain DLC items, (costumes mostly, and many never come out later for people who didn’t pre-purchase or purchase digitally) and so forth.
Finally, and I think most importantly, the theme wasn’t part of the stuff you got for backing the game on Kickstarter, so there’s literally no reason to expect to get it. It’s an item exclusive to purchasing the game from the PSN store, and wasn’t mentioned in the campaign or in any of the tiers of backer items. We got things like Chaoseater, combat portraits, and the like.
And I say again - I would like to have it too. It pains me to this day that I couldn’t get the NieR Automata pre-order theme as it is arguably the best one I’ve seen, and is significantly better than the ones that came out later for everyone to download, but I wasn’t about to play Sony’s game and buy their digital copy AND the 200 dollar black box copy from Square-Enix, but that’s just how it goes unfortunately. Sony’s tight-assed with the pre-order PSN bonuses 90% of the time.