I agree.

The main benefit of being familiar with how data structures and algorithms work is that you become familiar with their runtime characteristics and thus can know when to reach for them in a real problem.

The author is correct here. You'll almost never need to implement a B-Tree. What's important is knowing that B-Trees have log n insertion times with good memory locality making them faster than simple binary trees. Knowing how the B-Tree works could help you in tuning it correctly, but otherwise just knowing the insertion/lookup efficiencies is enough.