If you frame it as just "extra knowledge" then, sure, it's not a weakness. The problem is when extra knowledge is acquired at the expense of deeper focus (knowledge) in another area.
Just as an example, if you look at tech job postings you'll see that they almost all want someone who is an expert - mostly senior level, have a core tech listed in the title (eg Senior React Engineer at Company X). I rarely see any truly general roles posted. People want "T" or Pi shaped devs, nobody wants a "-" shaped dev.
As a dev with 10 years experience and a masters who has not been allowed to specialize due to language/stack/project/product context switching, I can anecdotally say that generalists are not valued and that this breadth of learning generally prevents specialization. I am only a midlevel and make under $100k in a moderate-high COL area.
Being a generalist is beneficial in freelancing, since it gives you demonstrated skill in lots of areas. The more areas, the more projects you "qualify" for, since clients want assurance that you can jump right in and be productive. (Also, "getting up to speed quickly in a new language/codebase/whatever" is a useful skill in freelancing, since that is a clear need)
I think people hiring employees frequently don't realize that they need generalists and instead act like they are hiring permanent contractors.
You've made the strongest case I've seen for some knowledge flexibility by bringing up tech freelancing, but this generalization is still ensconced in tech specialism. The last two posts have lost sight of the bigger picture.
The conversation began with the OP talking about wide cross-disciplinary pursuits.
"A couple of years back I started dabbling in the social sciences and humanities (my background is in ecology / evolutionary biology), and became interested in one discipline after another. From psychology to history of science to anthropology and sociology, to economics and politics, to philosophy and religious studies and cultural studies, etc."
My post was a reply to a response to "Refuse to Choose" and the concept of a "Scanner", someone who is looking at many different disciplines that do not all immediately relate to one another.
And my original post was to the effect of "Yes, being a scanner is a weakness if you can't synthesize your cross disciplinary knowledge into extremely valuable non-obvious insights and/or awe-inspiring products".
Basically, think of ideas as being distanced apart from each other. Some of them are in your head, others in mine, some are in a book, or a movie. If we are specialists working together on a project, then to access and synthesize ideas that exist in both our heads we need to have a meeting, which takes significant time. To access it from media, we're going to need to consume media and study, which takes even more time. A helpful analogy would be the memory hierarchy if you know a bit about computer architecture.
But, if many different ideas exist already, only in one person's head, no meetings are needed. They can just work, synthesizing as they go. That is where the "Scanner" emerges from their cocoon and inverts what has been up to then a weakness sapping the ability to excel in one field, instead becoming what one might call "A Renaissance Man".
