S3 Direct Upload animation not consistent

When uploading a binary files via the import dialog and when S3 Direct Upload is activated, the upload animation overlay on the file icon is visible (a % progress from left to right) and is proportional to the amount of data uploaded. This is great as I have the ability to judge how long the upload(s) will take.

However while the uploading is in-progress, if I click on the "Add Properties" button to begin entering metadata, the animation changes to a cyclical/looping progress bar, without any ability to tell the real progress. This is the same animation I get when S3 Direct Upload is not enabled.

I would expect both animations be the same, showing a linear bar and % uploaded.