The new cover art scaling feature is a bit weird, it kinda makes sense in Playing now > Player view, as if you have a really low resolution cover image, you might not want it stretched. But in the small display section it's not functional because:
strech:
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100%:
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As you can't change the height of the display section, you are either going to see just a small part of the full resolution cover. Ideally you would be able to change this display section height (as I think the height is too short for high resolution monitors), or to have the cover always stretched in this window.