Patch Queue Documentation restricted

When I click 'fork' on a mercurial repo, bitbucket helpfully informs me that I could create a patch queue instead. Since I'm not sure what the implications of that would be, I click the documentation link right next to the form, only to be asked to create an Atlassian ID (don't I already have one, being logged into bitbucket), and then the page turns out to be locked down so I can't see it. What gives?