USkeletalMeshComponent::CalcBounds updates CachedLocalBounds by transforming the world FBoxSphereBounds, by the WorldToLocal transform, which is not sufficient to calculate the bounds in local space. This causes the bounds to be incorrectly expanded.
Enable visualize bounds in the viewport.
Place a mannequin in the level.
Enable 'Component Use Fixed Skel Bounds' on the mannequin.
OnTick, call InvalidateCachedBounds followed by CalcBounds, drawing the results.
Simulate in the editor and rotate the mannequin.
Expected: The both bounds should match.
Result: The bounds displayed by the viewport setting are incorrectly expanded.
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-73089 in the post.