That's fine and all, but where's the bug you're talking about? There's nothing wrong in your pic.
When converting YUV to RGB, it's a matter of choice if you replicate the subsampled UV planes 1:1, or if you interpolate during resampling. The former is what Avisynth and ffdshow(default) are doing, the latter is what ffdshow's HQ=true does.
Both methods are valid, there is no "right" or "wrong".
Definetly, it is not a bug. A missing option, yes. But not a bug.
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