I haven't heard about Tony Vaughn before this post but as far a I know that Bitcoin's price was still over $13 a single Bitcoin and if that person might have hold his Bitcoin then he would be a millionaire right now. If we think about that in logical perspective then we get the answer that the guy didn't hold his Bitcoin because he received his Bitcoin as salary and mostly we spend our salary on the things that we like and that guy might has converted his Bitcoin into fiat so he could purchase the things that he needed during those days.
Based on some news I read, Tony got his salary in Bitcoin when its price was $1,181 on the Mt Gox exchange. It's true that back then, the price of Bitcoin had a really big jump, and this event from a decade ago actually made a lot of people talk about Bitcoin. In early January 2013, the price of Bitcoin was about $13, and later in Q4 2013, it reached its highest price at $1,000.
So, to sum it up, the experiment of receiving a salary in Bitcoin started during a time when Bitcoin was doing really well in the market. This was partly because of something called "halving" in November 2012... and usually, in experiments like this, salary payments weren't done many times... maybe just once or twice. So, I don't think Tony Vaughn became a big millionaire from his salary back then unless he held onto his Bitcoin until now.
Personally, I'm not a fan of discussions about regrets, like "if you didn't sell coin A a few years ago, you could be a billionaire by now." It's better for people not to dwell on their regrets and focus on the future. Bringing up past experiences that sound like big mistakes is not really ethical.