Wikipedia 1. d4 d5 question

http://en.wikipedia.org/wiki/Closed_Game
^Found here is a statement in the intro paragraph that says that, and I'm paraphrasing, in d4 d5 games, the fact that there are different variations one can transpose to is more consequential than the fact that there are transpositions one can make in openings with 1. e4.
So ...
What exactly is more important about this concept of transposition in games that are closed than in e4 games?

The relevant quote from that source is "Also, compared with the King Pawn openings, transpositions between variations are more common and important in the closed games."
Question: Why more important in closed games?

Off the top of my head, a closed game isn't as dynamic or fluid, so whatever position you end up in after the opening, that's the way the board is going to look for a while.

you are probably the funniest guy on chess.com

I'll agree with Ivandh that stuff like the pawn structure won't be changing very quickly. So the overall character of the game won't change as quickly as in most open games, when pawns tend to get traded off earlier, and piece are flying all over the place.

As for the transpositions in the original quote, it just means that there are more ways to get to similar positions. For instance 1. d4 d5 2. c4 e6 and frequently 3. ... Nf6 is a common way to play the Queen's Gambit Declined. But after 1. d4 Nf6, black can still end up playing e6 and d5 soon to end up in a QGD, rather than going with a typical Indian opening.

That won't happen as much with the sharp open lines. This doesn't happen as much with open lines, because you're more likely to trade off pawns or pieces very early, in ways that don't duplicate the results of a different opening.

But there are definitely transpositional possibilities in the open games, too.

basically.. 1.e4, c5 and no matter how hard you try you can't turn this into a caro-kann or a french or a ruy lopez (and the same for each transposing to the other three). most e4 defenses diverge on move 1. many d4 defenses don't diverge significantly for many more moves. 

Actually, the French and Sicilian can transpose in certain lines, but it doesn't happen frequently. I've done it, in both directions.

For instance, I once started a game with 1. e4 c5 2. d4 trying to play the Smith-Morra Gambit against the Sicilian, and my opponent wimped out and played 2. ... e6 to defend his c5 pawn with his bishop. He eventually ended up playing d5, and it turned into a mainline French.

Similarly, after 1. e4 e6 2. Qe2, it's usually said that 2. ... c5 is black's best response, transposing to a Sicilian where white's queen is misplaced. The reason this opening works so well for white is that most French players as black (myself included) just don't know the Sicilian well enough to actually do this, so they keep on trying to play it like a normal French, often with disastrous results.

@fromper: yeah of course there are going to be exceptions, the uncommon alapin can transpose to a french quite easily, but in the vast majority of cases such transpositions simply do not happen. thanks for pointing that out though. 

For awhile my main defence to 1.e4 was the french, then changed to e6 sicilian, i.e 1.e4 c5 2Nf3 e6. For anti-sicilans like alapin chould use French variations. In English club chess OTB games it is typical for players to avoid main lines like the plague. So chould make opening switch without losing so many games, and gradually learning more sicilian type solutions.