It is interesting to see how the author view seniority in programming. In most places, seniority comes with years of experience. One thing that is different in Computer Science than in other field is the constant evolving of the tech, language, framework, and tools. Having years of working in the field and eventually you may become obsolete if you don’t try and constantly learn new stuff. A person that is entry level might know more about the latest node.js technique than a senior developer.
However, seniority does not just mean how well you can program. Seniority can also mean you know how to communicate effectively, how you work well with team, how well you can lead other people. An entry level developer may have better coding skills than a senior developer but I doubt he has other experience that may be critical in a company.