When Link Building Should Niches Be Related?

So, I've recently been working with a client who provides me with the article tittle, keywords, and anchor text. However, his anchor texts are sometimes weird if I can say so. For example, I just worked on an article whose main keyword was about healthy eating. And I was to add a link back to a dating site using the anchor dating reviewer. Healthy eating and dating sites are two different niches. Hence, my question whether it's good for your SEO to link back to niches completely different from your niche.

not good... I mean, your client's website won't get penalized for this, but it's a wasted linking opportunity

For tier 1 links the niche should be related or you get hit by google penalty. It won't look natural for you to create a backlink from a gardening site to a site about computers.

From what I have studied, the links must have an Anchor text that fits the niche or topic of the article.
Otherwise the link will have little value and will pass little traffic juice

It's not good, these links and anchors can harm your client's website.