Completely agree it is both a usability and accessibility issue and both do matter. Even if you only took the big stick approach that you shouldn't have a choice about accessibility as it's is a legislative requirement in many countries now.
If someone is scanning text, then a single word here doesn't stand out or register against the keywords they're looking for. Especially so now, with sites styling without underlines for links (the whole idea of which is to make readers aware it's a link - whether it looks pretty is important but secondary to comprehension, and color alone isn't enough). If you underline the phrase, which should directly indicate the content of the page the link goes to, that makes it clear to the reader what they'll get when the click. Just apply the Steve Krug "Don't Make Me Think" principal - people just want to get to their destination quickly without thinking much about the journey there, and your job in creating that site is to help them succeed.
BTW, accessibility issues affect a hellava lot more people than those using screenreaders (and more than just sight issues too). Some 10-20% of the population have poor sight and scanning is harder you want those link words to stand out, which just using here doesn't do. The growth of accessing the web on phones has just massively increased it as seeing, let alone trying to tap, a tiny single word is really poor usability. That's a pretty big part of anyone's target market to decide you don't want as potential customers just because you make it harder than necessary to use your website.
None of that means your site can't be attractive, but people don't primarily go to a site because they like how it looks, it's to do something. Using words they are scanning for will help them do this.