Valhalla doesn't need to run at 1620p 30 fps, devs were lazy and used the same 1620p-2160p scaler on Series S, Xbox One X, PS5, and Series X, because 1620p is over the 1080p-1440p recommendation for Series S, Ubisoft had to drop to 30 fps. It could definitely run the game at 60 fps, most likely with a 1080p-1440p dynamic scaler, if Ubisoft cared to take the time to implement it.
As for no ray-tracing on Series S for DMC V, considering it is terribly optimized on both PS5 and Series X, I'm guessing they didn't want to take time to optimize a 3rd version of the game when they were already struggling to optimize 2 versions. Doesn't help that they decided to target so many different performance profiles, they have 4 different performance profiles per platform to optimize on XSX and PS5. It's just too much work for a small porting team that is facing covid production issues.
Also it's worth noting that we have reports from several sources that the Xbox SDK was behind schedule and came in hot, only giving devs a few months to get used to Xbox Series development ahead of launch. I'm guessing that played a factor in these Series S launch game issues as well.
The good news is that several of these launch games and next-gen updates for last gen games show performance on Series S runs as expected, 1080p or 1440p at the same framerate as Series X runs them at 4K, exactly what MS designed Series S to do. Yakuza for instance, it has one of the most demanding game engines of any of these launch games, the Dragon Engine, and yet it's managing 1440p at the same framerate as Series X at 4K.
Thanks for the explanation. It's this kind of thing that makes me sometimes became a pc gamer. How difficult it is for the devs to give us the option? Why cant I choose to run at 1080p 60fps? I really dont get it.