[joe_the_user]

I'd offer a similar criticism. The problem with "our working memory has a maximum capacity of roughly 4 [chunks of information at once]" is that the units ("chunks" was original) winds-up undefined and moreover it tempts one just divide whatever a person seems to be able to process into four things and call them units.

And the way I'd see your "funnel" criticism applying is that each student can easily begin with a different set of mental tools, some of which let them take an idea as one relatively small "chunk" and some of which might process the idea as several "chunks".