And your stance of “I can learn x in two days, so how can people say it takes longer to learn y” isn’t pretentious?
When do you consider someone’s “mental model” “appropriate”?
“appropriate” isn’t a quantification of the mental model in itself, I am using the word as “having a mental model that is appropriate to the thing being learned”. A different mental model is required for React than working with vanilla JS and manipulating the DOM directly, so the mental model for one isn’t appropriate for the other.
And yes, a mental model is quantifiable, to the extent that it accurately predicts what consequences design and implementation decisions may have on the behavior of the system.