When uploading attachments via the link tool, there are three steps involved in doing so:

1) selecting the file via Browse

2) uploading the file via Send it to the Server

3) clicking OK to finish

In my opinion, step 2 should be automatically done, like in the attachment selector at the bottom of pages, which uploads files directly after selecting it. Involving step 2 is not very intuitive and I've seen many users struggling to understand the workflow immediately.