A page like Wikipedia:ANI, which is a shortcut page, has many links to it across Wikipedia; however, when XTools page history stats are run on it, the entries for "Links to this page" erroneously reads 0, as if no pages link to the shortcut page: https://xtools.wmflabs.org/articleinfo/en.wikipedia.org/Wikipedia:ANI. However, Special:WhatLinksHere/Wikipedia:ANI clearly shows that there are indeed links to the page.

On the other hand, if we choose a mainspace article, such as (for a random example) President of the United States, the tool does output a reasonably sized number (in this case 28,163 at the time I'm writing this): https://xtools.wmflabs.org/articleinfo/en.wikipedia.org/President%20of%20the%20United%20States

Incidentally, on the legacy version of XTools, the links counter says 0 on all pages, including mainspace ones. See President of the United States: https://tools.wmflabs.org/xtools-articleinfo/?article=President+of+the+United+States&project=en.wikipedia.org