Correct, Alan Wake 2 was funded by Epic Games and was first unveiled at the PlayStation Showcase event. Why was the PS5 used to unveil it? You're not going to showcase your game on a console that's farther behind in development, but the point is, I wanted to remove any doubt, such as the assumption that Epic is giving preference to Microsoft's console, when it's more likely that PS5 would get the better treatment.
At the end of the day, you did answer the question. When a game is developed with PS5 as the lead platform, developers establish a baseline that the other platforms follow and don't necessarily need to exceed. Even if Series X has slightly more horsepower and more advanced features, for example: Hardware-enabled VRS; because the PS5 doesn't support it (PS5 Pro will) it will not be supported. Just an example, not saying Alan Wake 2 uses hardware VRS, just pointing out how using the PS5 as your base is a negative for XSX. However if you're pushing a high end PC with your engine, then other platforms will have to do their best to keep up, the closest being XSX, followed by PS5 and far behind XSS as it should be.
Imo, Alan Wake 2 serves as a good example that when you push hardware beyond its current limit, you tend to find the weaker links down the line, as opposed to a well optimized game designed to run great on the PS5, then maybe not getting the best optimized code on Series X for the same game that's not really pushing any limits beyond the capabilities of the PS5, another would be Immortals of Aveum which can bring even a high end PC to its knees, that game also runs best on high end PC, followed by XSX, PS5, then series S far below just as the performance difference is expected to be.