So, the criticism here is why a book called 1.d4 d5 did not actually analyse 1.d4 Nf6? 

I get the point, honestly. But one of the core ideas of the book was to show that Black has nothing to fear in the Exchange Variation. The original idea, a few years before the actual book happened, was to analyse 1.d4 d5 2.c4 e6 3.Nc3 Be7!?, when I "discovered" the power of the h6+Nh5 plan, we decided to go for this instead. I am happy that after 4 years, the whole repertoire still goes strong (I even actually sent a few updates for the latest reprint a few months back).

Somewhere and somehow you have to fix, set and keep a standard!? And there are other ways than statistics ...

1.d4 d5 2.c4 e6 (3.Nc3 Nf6) is 100% the historical, the established, the classical way to reach a QGD.
Therefore it‘s also the ECO classification, based on important games up to ~1965 .

In that sense 1.d4 Nf6 is only a very important transposition tool and its value depends on several things. Maybe it‘s the Nimzo, maybe the QGE, maybe the Tromp, maybe the subtil difference between Blackmar and Hübsch ?!

tracke

I find your database "analysis" to be quite superficial. Why did you stop after 1.d4 Nf6 2.c4 e6 ??? You needed to look deeper. Using ChessBase Big Database 2018 and taking games from 2007 and later we find the following numbers of games:

------------------------------------------------- 
44.032 := position after 1.d4 Nf6 2.c4 e6 3.Nc3 d5 
31.780 := last move was 3...Nf6  
10.637 := last move was 3...d5  
------------------------------------------------- 
66.163 := position after 1.d4 Nf6 2.c4 e6 3.Nc3  
10.637 := black plays 3...d5 
50.555 := black plays 3...Bb4 
------------------------------------------------- 
55.198 := position after 1.d4 Nf6 2.c4 e6 3.Nf3 d5 
18.113 := last move was 3...Nf6  
19.515 := last move was 3...d5  
------------------------------------------------- 
73.149 := position after 1.d4 Nf6 2.c4 e6 3.Nf3  
19.515 := black plays 3...d5 
28.190 := black plays 3...b6  
15.682 := black plays 3...Bb4+ 
-------------------------------------------------

From the above we can easily see that black is mostly using the 1.d4 Nf6 2.c4 e6 move order to play the Nimzo-Indian -- after 3.Nc3 the Nimzo is 5x more popular than transposing to the QGD. Even when white plays 3.Nf3 to avoid the Nimzo, only about 1 in 4 blacks transpose into the QGD, although theory considers black has better equalizing chances there than after 3.Nc3. We haven't even touched on the Catalan with 1.d4 Nf6 2.c4 e6 3.g3, but I will note that 1.d4 d5 2.c4 e6 3.g3 is nothing for white, so the 1...d5 move order at least forces white to commit to Nf3 before g2-g3. To summarize, when black wants a QGD, the 1...Nf6 move order is common enough, but the 1...d5 move order is more popular by about 5 to 3.

Your final point beginning "Furthermore" is irrelevant to your 1...d5/1...Nf6 question, because 1.c4 and 1.Nf3 are choices for white, not for black.