The main reason to make a search engine Browser is because browsers, and specially Chrome are very aggressive against search engine extentions (chrome insists in warning users their search engine changed). Also, search engines pay a fat share of revenue to browser vendors in "default search engine" partnerships.
If you just opened the article, you would have read that it uses the system-provided engine, so WebKit for MacOS and eventually Microsoft-flavoured Chromium for Windows.
Imho they shouldn’t waste resources on a product that no one asked in an already competitive market since they’re not adding anything new.
Woah... My bad! I read Mac but for some reason thought of the iPhone, in which unless things have changed, Apple doesn't allow any browser that isn't built around their technology. Too late to delete the post, unfortunately. Apologies.