468060 (64) [Avatar] Offline
#1
On p. 31 it says "the .enter() function tells D3 to .append() a new div when there are more elements in the array than elements in the selection."

The .enter() method doesn't 'tell" D3 to do anything. It returns an object containing placeholders. .append() then attaches DIV tags to each of these. Given that this is a step-by-step process, with each stage working on what was returned by the previous one, it's important to be clear what does what.
elijah.meeks (123) [Avatar] Offline
#2
I think the wording the way it is, even if it's not as exact, will make more sense for someone getting into D3. Anyone who is more concerned with the internal structure of how D3 works won't be confused by that wording.
468060 (64) [Avatar] Offline
#3
I agree that people might not be interested in knowing the internal workings of D3 (I'm not). However, when there are steps which have to be followed in various combinations it's important to know what step does what.