Let us avoid tilting at strawpersons. The author does not claim industry professionals shouldn’t know jargon. From tfa:

So for general use, I recommend against using a11y, yet I’ve named this site with this acronym. There are a few reasons I made this decision. Firstly, WCAG 3.1.1 does permit domain-specific jargon so long as it we define it. So, take this post as a definition. Additionally, I expect most people who have found this site will have found it because they are specifically looking for something accessibility related.