Linux gaming is a little hit or miss. Some games have a performance boost. Some are about the same. And some games perform worse. This is the reality. And this is what should be expected.
Your post is still true for your specific hardware and this specific game, with these specific drivers, but let's not go crazy here. Linux is good, yes. Fantastic even, on the Steam Deck. On PC most people are better off sticking with Windows, especially if you play a couple of competitive multiplayer titles. Or if you want to stream games from one device to another in house. Or if you have limited time and just want shit to work. Linux is getting closer, but the out of the box experience need to become way better and I don't doubt it will sooner rather than later.
This went south, east, north and west at the same time. Calm down people :)