I don't think this necessarily has to do with hyphens. Because the argument holds for most keywordkeyword domains too.
But as to why he would say "keyword-keyword domains," rather than "keywordkeyword domains" my guess is one of the following.
- Hyphens are still important in the url-directory. mysite.com/mystory is worse for SEO than mysite.com/my-story.
- "Keyword-keyword" is a bit easier to read than "keywordkeyword."
- The hyphen makes it look worse due to their lack of use.
Either way I do see his points here.
- For professional businesses brands are the go-to SLD. Sometimes a PMD or an EMD does work as a brand, but if it doesn't then it may come across as a low-quality site for diverging from the norm.
- This is also true. A perfect example is when zenpayrolls.com wanted to expand and rebrand to Zen, they couldn't secure the domain and ended up rebranding to Gusto.
- While I think he's right, there's a caveat I think he's missing. From a competitive perspective nike.com is better than shoes.com*. Because people searching for "shoes" will find nike.com but not shoes.com, and at the same time, people who want to look for nike-related products will be able to find them by adding nike, e.g. "nike jersey". So in that he's correct. But! Like I hinted on in #1, something like "Manhattan Plumbing" is an extremely effective brand in terms of marketing. You can literally put up an ad only saying Manhattan Plumbing and nothing else, and people will know that your company exists, where you're located, and what you're doing. And if your brand is Manhattan Plumbing, then you want manhattanplumbing.com.
*shoes.com redirects to dsw.com, and you receive no SEO-bonus for redirects. In other words, aside from the occasional http-search, shoes.com is wasted.