>I think they underestimate the value of specific knowledge

This is the crux of the issue. When it comes to "Knowledge Work" almost every step sooner or later becomes a specialization. For example, I used to sneer at the role of a "Build Engineer" until i was forced to take up that role in one project. The combination of HW Platforms, OS versions, config switches, build flags, magic incantations etc. quickly gave me a new found respect for a job which i had considered "trivial".

I find that doesn't really capture the difference. In programming, the building part is fully automated. You press play or type a compile command and wait. If someone wants a build estimate, you should give them the time it takes to compile an deploy. Code is blueprint. Writing the code is all engineering, R&D, design and architecture and it usually entails figuring out how the system will interface with countless protocols, legacy systems, details of user's lives etc. It's nothing like building something that is already fully planned. It's a lot more like researching and planning all the details.

And they overestimate it when writing job ads.