Majority of GameCube games don't support 16:9 so Auto set the screen ratio to 4:3 no matter what. Dolphin can't detect when you are using the 16:9 option in a GameCube game so you to set it manually in the video panel.
From France with love.
Laptop ROG : W10 / Ryzen 7 4800HS @2.9 GHz (4.2 GHz Turbo disabled unless necessary for better thermals) / 16 Go DDR4 / RTX 2060 MaxQ (6 Go GDDR6)
Laptop ROG : W10 / Ryzen 7 4800HS @2.9 GHz (4.2 GHz Turbo disabled unless necessary for better thermals) / 16 Go DDR4 / RTX 2060 MaxQ (6 Go GDDR6)