It's a factor and not the sole factor. Saying it's "by definition" is incorrect.
> The author does a poor job of justifying why these pop-cognitive-psych theories should have more weight than prior exposure.
There's no reason to believe either way, except one path has decades of evidence. Human behavior is not overcome by programmatic "elegance". The dismissive "pop" prefix is signaling bias.
> no magic keywords and syntax to memorize
ie no syntactic sugar. Pointless repetition is counter productive.
>a there's no [logical] way to fall through >b [no way to] forget an else, >c expressions instead of statements >d no early returns
b. The interpreter catches it. d. Pointless execution is counter productive.
> literally everything about the Lisp example is more readable to me
That's a single data point. Statistically it's worse, but you're practiced and apparently still physically able to quickly discern the nested count (or use an IDE). Yet another example of a position that is counter to existing studies. Heavy nesting is error prone, even when a program compiles (eg Monden et al., “Evaluating the Applicability of Reliability Prediction Models between Different Software,” ISSRE 2001)