You’re arguing with someone who has 40+ years in the software business, including hiring and building teams. And 15 years freelancing, so I know about diving into code with no training.
The process implied by the post may represent the most efficient way to fill chairs. It does not, in my experience, describe an effective way to build a team or a product. Putting the focus entirely on “tech stacks” backgrounds the actual goal of adding value to the business. Competent programmers can learn new tools quickly, I have never observed that as a blocker.
Programmers complain constantly about job postings that focus exclusively on very specific technologies, as if knowing Postgres excludes them from learning MySQL in a week, or having used Python means they will need years to get up to speed with Ruby. I agree. Cast a wider net selecting for competence and experience and curiosity rather than a shopping list of mostly ephemeral languages and tools.
The extremely high failure rate of startups, and dissatisfaction with hiring and retention practices, should give hiring managers and recruiters pause. No one you might want to hire likes the tech stack focus, and it doesn’t seem to work very often.