Doesn't even have to be anchor text. It can be text on page B in the general vicinity of a link to page A. I don't know if they do this all the time, or only to pad the SERPs when you've looking for something especially obscure.
Ranking signals used by the algo and content are surely two different things.
That's not my understanding, BeeDeeDubbleU. There is a major part of the ranking algorithm that attempts to measure "relevance" and that depends on content quite a bit. It gets combined with the backlink metrics, trust & authority and so forth for a final ranking score, but it's still assessing content.
My impression is that anchor text is treated similarly to page titles and headers. The words are given somewhat more weight than normal text words. But everything is combined together to get the final assessment of the overall content of the page.