The documentation is outdated. That's no longer part of the Bitbucket overview screen. When it was, it didn't make any effort to detect whether SourceTree was installed - SourceTree doesn't integrate into the browser. The closest thing is that it registers with the OS as an application that can handle URLs that start with the sourcetree:// protocol.
The easiest way to clone from Bitbucket (empty repository or not) is to use the Hosted Repositories feature.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.