I don't believe that answers the question, as I have the same issue. I, too, have a HR role and need to restrict people in that group to only being allowed to edit a particular page. The problem as stated is, when I break permissions for that page and add the role to that page to edit, there is no Pages tab at the top, NOR is there an option to edit the page when browsing the front-end.
It seems that the expected behavior is from the perspective of the HR user who is logged in: if I am in this role and have permissions for at least one page to edit, I should have the option to navigate to that page.
It seems the only option to get this Pages tab to show, is add the HR role to "Permissions for all pages", but explicitly deny access to every single page. Obviously this is a nightmare.
So, to accomplish this, what is the solution? Thanks.
EDIT: it also seems that even if I just have editable permissions for the HR role on a specific page, that user STILL cannot access the page (it throws a 500 error). Say, the /careers page is the page in question. If logged in, the user cannot access /careers/action/edit in the back-end, even though this HR role has edit permissions for that page.