The major reason I dislike showcasing open source contributions is that not everyone has either the time or the inclination to do so. Sometimes at the end of the day, engineers just want to do something else rather than glamming up their occasion out-of-hours hobbies.
Also, and I think I hinted at this in the article, once open source becomes a nice-to-have many people approach it in the same way as learning interview question solutions by rote for interview. How long will it be before you can buy ‘commits’ just like you can buy likes or followers on social media?
Many of the accomplished engineers I know myself either don’t have an open repo to showcase or choose not to and let their history speak for itself. Problem being, as you rightly say, you can’t share paid work.