Agreed. I think I shouldn't put hard boxes around languages like 'puzzle language' vs 'abstraction/clear thinking language'.

What I was trying to point at was more specific: the way I experience APL thinking tends toward 'expression search' and 'notation compression', which feels, to me at least, somewhat at odds with clarity about the underlying problem. More often than not, I seemed to produce an APL-shaped model of the problem rather than a problem-shaped model expressed in a language.

When I first learned about APL, I was looking for new ways to think about computation. What I found was a language that rewarded deciphering APL programs and generating clever new ones. That is interesting and beautiful, but it was not quite the kind of brain-rewiring I was looking for. My original comment was targeting people in a position similar to mine and trying to set expectations about what they would learn best from APL. APL may change how you think about array expressions and how far they can go, but TLA+ is much closer to what I'd recommend if what you want is clearer thinking about programs, systems and state.