It's a backlink game.

Create a new site that is of some public good like this site. This site will probably gain domain and page authority much quicker than their main site and will attract more visitors and the key is that their page is linked through this auth.wiki site so their page (logto) will get the SEO benefit as well.

But personally I don't think this is an SEO play, more like a brand awareness thing. Some engineer at logto probably got pissed off with the state of auth documentation, went to his boss and proposed creating a simple static site with the "business case" being brand awareness and SEO.