That only mitigates the problem of the official launcher not existing for Linux. Games are still installed with Proton.

For example, I was trying to install Into The Breach, which is available on both Steam and Epic. Steam has builds for all platforms, while Epic only has the Windows build. If I install the game using Heroic, it installs it with Proton, resulting in worse battery life and performance compared to the native build. Which is what you want to avoid with handhelds like the Steam Deck.