The notice comes from the official Moss account on Twitter; the only English language news source I could find about it at the moment is from Perfectly Nintendo, which translates the patch notes as follows:

• New Rendering Speed (Frame Rate) Selection Option Players can now choose their preferred rendering speed for smoother gameplay performance.
• New 54 FPS Setting Added In addition to the existing 60 FPS option, a new 54 FPS setting has been added, offering players greater flexibility in how they experience the game.
• Minor Display-Related Bug Fixes Several small visual and display issues have been corrected to improve overall presentation and gameplay stability.

Hopefully existing players can confirm the patch is live, and has improved the game's performance!