This is an interesting myth, but certainly a myth. I guess if we consider technical skill to be intimate knowledge of the latest fad framework, that might be one source of the myth. But that's not technical skills, just trivia about an implementation detail.

The fundamentals like networking, process and memory management, databases and SQL, all change slowly and are very long-lived career-spanning knowledge.

It would mean that no engineer could ever aspire to become a parent, take a sabbatical, further their education, or experiment with alternate career paths.

But I promise you that that is not actually the case. In fact, it is often the engineers who've stifled every other part of their life that are most likely to struggle in their mid-careers and beyond.