It seems to be relevant to hiring and startups, that is, if you hire people for particular tech skills, or build your startup around some specific area of expertise, half of these skills will be irrelevant in 2.5 years.
On a personal level, the fundamentals will be useful for your entire career, and the more you know, the faster you will be able to get the skill-du-jour. But the idea is that on your résumé, expect to change half of the lines in your "skills" section every 2.5 years, even if it takes you no more than a few hours to add these lines.
It also brushes aside tech in industries like defense, aviation, assembly lines, etc... where you have big, expensive machines, certifications, and projects that span decades. I wouldn't be surprised to find some Fortran code somewhere in the foundries that build the latest AI chips as EUV lithography literally took decades of R&D before it went to production.