In Andersson's Catalan, it is difficult for black to achieve the c7-c5 pawn push, so the position is not as open and retreating the Q to c2 is only one tempo loss.
Very true also, It seems Nc6 is the major difference between the catalan and this (as the bishop isnt hitting c6), and Nc6 I just checked neutralises white almost immediately as the d pawn is hit.
So I was wondering why you listed the nd7 c5 line, is it actually best?
I don't know what GM's think is "best" after 1 d4 d5 2 c4 dxc4 3 Qa4+, but it just makes positional sense to me that 3..Nd7 will eventually support the counter break ...c7-c5. It just "has" to work. So, in the line 3..Nd7 4 Qxc4 c5 5 dxc5 e6 (not the illegal 5..Bxc5 --I can says "oops" cause I live near Texas 
) and white cannot keep this c5 pawn (e.g., 6 b4 a5 7 a3 axb4 and white's a pawn is pinned against the rook).
e6 is the third most popular response, but more than half as popular as e5. the QGA is less than a third as popular as c6, so it is rarely seen. I personally wouldn't be worried about QGA, black gives away its bid in the center, and if they try to hold onto the pawn, they instantly lose.
About 13% of e4's end up facing the French, according to your database of choice.
About 11.5% of straight 1.d4 d5 2.c4 QG's face the QGA, along with about 13% of those games where white chooses to delay c4 till move 3.
Not the same, but about on par.