With "Use Default Sample Rate" disabled, animations under 30fps get resampled to 30fps
Result: The 60fps animation is 120 frames and 2 seconds long. The 24fps animation is 48 frames, but is 1.6 seconds long
Expected: Both animations are 2 seconds long
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-45523 in the post.