Could just be age discrimination. I've worked with more than a few people who are very suspicious of people over 40 who are "still just coders," saying that it shows the candidate lacks ambition or they must not be that good since they never advanced to a more senior role like very-senior-principle engineer or management.
This is such a weird industry. Most current devs will be still coders when they are over 40. Only a few can make it to management or high level lead engineer roles. There are not that many openings for that kind of role. I used to work as mechanical engineer and there it was totally normal to have engineers who were 60 years old.
I understand your suspicion, however, I find it odd that the author couldn't code AND recorded a video discussing his code. It seems like he'd hide it away if he couldn't code.