I don't think this is a Clementine issue. From what I've read tagging tracks isn't that straight forward. I even think i've seen somewhere that it can even depend on how & on what the original tracks were tagged.
All I know is that using exfalso always seems to give me the desired results, & Clementine seems to be the best player for correctly reading those tags (in linux anyway).
At least you've found a workaround
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