This phenomenon receives its name from the premise of a pet "talking" parrot who is suddenly silent when guests are invited to see it "talk." "I swear!," says the owner, "He says all kinds of stuff! Our title-What is taught is what is learned! One would end up a 'talking parrot!' Learning, in dictionary parlance, implies gaining or acquiring knowledge/skill by study, experience, or being taught, while, Teaching implies showing or explaining to someone how to do something.
Learning is analogous to a zoom lens and wide angle lens of the camera (Douglas Brown), where, the wide angle conveys the overall picture (meaning), without the grammar et al; on the other hand, the zoom lens helps to focus on a selective area (pronunciation, vocabulary). Each picture distinctly brings out a specific detail. Barbara Oakley specifies two modes of learning-focussed and diffused, wherein, the diffused mode lets the mind wander, without paying attention to mistakes or specifics in contrast to the focussed mode, that examines something specific. Every individual does not posses the ability to comprehend and recall everything that is given, contrarily, every learner has the potential and motivation to apply the principles in the real world. Moreover, if everything that is taught is learned, all around would be robots, not humans with critical thinking.
Critical thinking involves objective analysis and evaluation of an issue in order to form a judgement, hence, a lot of learning takes place by exposure and experience, rather than mere instruction. Engaging in practice is more important than rule based learning, for the spaced repetition allows the brain to process information by spacing out learning.
As the adage goes, Practice makes perfect, not parroting.