My argument is that since "senior" has been used as "someone having a high status" for thousands of years, it actually means it.
If by "senior" you are referring to somebody who's been in the industry or on a project for a long time, I would agree.
However I do not agree that that person will automatically make a good teacher, team-lead, consultant, mentor simply because he/she has been around for a while.
Sorry if I was not clear enough in the article, I'd appreciate any suggestions on how to improve it so that it makes the point better.
Confusing or conflating "senior in age" with "senior in experience" is exactly what his post is about.