Unfortunately it isn't that simple. Interlace is annoying thing.
Filter panel scanlines may not match emulated Amiga scanlines and there is also RGB mask "scanlines". It is not guaranteed all users want them to be disabled in interlaced mode, also interlaced mode being active does not guarantee that mode is actually interlaced, some weird programs may cause flickering scanlines. (This won't affect Display panel scanline option)
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