that has nothing todo with deflicker, its just your tv doesnt like the raw interlaced ntsc mode which is totally understandable.
if you wanna check out deflicker in an actual game set the video mode to auto and open up melee, there in the settings you can disable and enable deflicker to see its effects on the graphics live. Its just an option I found was pretty neat since it looks much better for me with deflicker off so I thought I would implement it for all games via nintendont.
yes, it is the game default and cant be disabled in anything besides melee normally, pretty weird setting, no idea why it was only in a single game.