This is a really sloppy summary. First, the given example is broken (the numbers in the nodes change from fig 1 to fig 2). Second, the delete operation is only like the insert operation if you look at it from a distance, squint, and tap your heels together three times. Implementing the delete is about an order of magnitude more difficult than the insert, IMO. An article on the details of that would be enlightening.
(Personal anecdote: in college, I spent a nightmarish two days implementing the delete operation on a B-tree, because I had put it off until the last minute, thinking that it was "just like the insert, but with contractions". I was wrong. I don't think I've spent that much consecutive time in one chair before or since....)
(Personal anecdote: in college, I spent a nightmarish two days implementing the delete operation on a B-tree, because I had put it off until the last minute, thinking that it was "just like the insert, but with contractions". I was wrong. I don't think I've spent that much consecutive time in one chair before or since....)