One thing that you haven't touched on here (and most people don't) is that "professional experience" is highly nebulous in a field like software development where you may have a >10 year head start compared to your peers in terms of life stage.
I started programming when I was 8, and have been a contributor to many software projects from age 11 onwards, with a lot of those contributions still publicly visible on my GitHub profile. Straight out of college, sure I have "~1 year of experience" (that is, if you even count my internships) but I've been programming for more than half my life. If you sum my ad hoc experience contributing to FOSS projects, doing one-off contract work, personal projects, and just tinkering over 15 years I might very well be as good as someone with "15-20 years of broad industry experience", but it doesn't show on my resume as an easily quantified number. I've definitely come across and worked with these kinds of tenured, experienced workers who went into software development not as a hobby or interest but as a mere career and ended up falling behind in their later years due to a lack of drive.
This kind of thing is rare in most professions, so people aren't used to it (and I'm not saying that it's 100% what's happening in your anecdote), but I believe it is becoming increasingly common in software development.