what else can anchor text helps us navigate better mean?
they specify the text which we know doesnt make any difference to the ability to navigate, only to supply relevance to those links. So yes i also read that as make the text bang on relevant to the page you are linking to. Down the road this has become a point to downgrade you on, too much relevance or repeated terms across navigation when thats originally what they said to do.
So what made sense and to me still does, the keyword being in the title, links, meta description is now more likely to see you NOT rank. Because only webmasters clued up go each detail bang on google then decided to dial down the scoring if you score too much. The funny thing being this meant only webmasters even more clued up then the other clued up webmasters got a sense of the middle ground now being the high ground and thus the middle ground became the true seo'd ground.
So i ask what does over optimizing really mean? It just means falling foul of the algo, nothing more technical than that.