No, they're not. It causes the lists to be sorted alphabetically, thus it only works if you have a number in every title. If you have correct metadata, it actually breaks the proper order.

Moreover, I've got 5 files: "101.mp3", "102.mp3", "103.mp3", "201.mp3", "202.mp3". They have no metadata and in the browser they are displayed in the correct order (it's only 5 files, might be random ). Maybe it's not just that you don't have track numbers assigned, but rather have them assigned incorrectly.

So, I'd rather say check your metadata.

Edit: Yep, it was random.