enabled extended gui makes resets all Video mode settings in menu to default
Video, Deinterlace -> Blend. Settings, Extended GUI -> Enable. This will turn off Deinterlace!
Video, Deinterlace -> Blend. This will function but will not appear in the menu.
In conclusion having the Extended GUI enabled switches off Deinterlace and will make the menu options not conform to the status of Deinterlace mode.
Edited by trax