Whoever this AE is, he's partially right.
Information is not knowledge, it must be mentally digested and often practiced or used for it to become that.
Those who read too much lofty theory are often out of touch with reality, as a result of reading too much and thinking too little.
However, this has nothing to do with age, in my opinion.
Theory and practice are inseparable parts of a whole, working system.
The separation itself is an odd thing, indeed.
Which sort of is akin to the separation of opinon/belief and action.
Yes, the foundation of knowledge at an early age usually starts out with books, quite generally.
Stories, songs and today television are also sources of inspiration.
To further drive home the point of theory and practice, though...
Does not kids often go out and reenact the very things they have read about, or derivatives of what they have been told through books?
Whether it is cowboys and indians, knights and monsters, soldier versus soldier, spies, kids playing doctor...
Through this "practice" the children gain a deeper understanding of what these things feel like.
Through their imaginations they can bridge the gap of being shot with a peashooter while the adrenaline is pumping to what it feels like to be in an actual battle.
Without this, the little stories about soldiers fighting or doctors saving lives would probably mean very little.
Books, though, seem to create individuals with a more in-depth understanding of things, though, compared to the kids who are brought up only with television.
Those kids often seem to turn out less imaginative and knowledgeable, somehow.
My conclusion based on my own observations is that your assumption is correct.
In my world-view literature is the foundation of knowledge.