1. This doesn't preclude devs from doing this very thing, limited dev kits or not. There are still SDKs that can be used to create a simple app for trailers. You don't need an HDK to build a simple trailer app. Abandoned may be a realtime trailer ala 3DMark, but having an app for IndieGameX, that just features a bunch of trailers, is another marketing channel that doesn't cost a thing, as you note. The mere presence of the game logo and name in the store is a form of marketing.
2. You don't think anybody is going to download the Abandoned app? You don't think people would download IndieGameX app, if it was the first of its kind, and appeared in the store for free? You're dismissing basic human behavior, and a simple rule of marketing. There's a reason SEO is so important. Get your product visible to people who are browsing, and you are guaranteed a certain number of clicks, just out of curiosity. You can lol if you want, but you're out of your mind if you think nobody would download a free app with a game logo on it. Getting users in the door to survey your app is what mobile ad campaigns revolve around.
Sorry, not buying it for a second. Unless PS5 owners are somehow immune to the basic rules of human gullibility and stupidity, then you're trying to sell an alternate reality, where there's no value in exposure. Any publicity is good publicity, and that's what placement in the store front is. Instead of just your game listing, you double your effort with a game and an app. I'd fire any marketing agent who didn't understand the basic value presented there. Why else do stores waste floor/shelf space with empty boxes of products? Because that's marketing. Increased visibility is like rule #1.