@Switch Blayde"Resized to fit", doesn't mean 'hack and sliced', instead it means, if it's an entirely different dimension (the height and width ratios being different than the one specified) it'll merely be scaled to fit. However, if the dimensional rations are off, then yes, expect something to get chopped off.
Which is why, when publishing, it's always best leaving enough 'white space' (visual area devoid of essential elements like words or publication information) as you can never count on a cover element not being trimmed, especially since, when it's physically printed in bulk, the pages (both the external cover and the interior pages) are typically printing in 14-page increments, so the interior pagination doesn't fit how it's read.
So, as a one-time visual artist/graphic-designer, I always keep those unanticipated details in mind, even now, a full 30-years on! Some things you forget quickly and easily, other stay with you, till the bitter end. ;)
Did you think my publication experience was entirely fly-by-night? As usual, I researched the hell out of it, way back when it once, and now, still matters.