Zuke Em section 4.2

In section 4.2 of Zuke Em, after 8.a3 Qc7, white can transition to the C-Z Phoenix directly with 9.dxc5. If white plays 9.Nbd2 (which I like since it opens c1 for the rook on a1) and black responds 9...b6, the book states that brings white back to the 4.1 line 8...b6. However, since white now cannot play Ne5, this line is no longer valid. The book seems to imply elsewhere that 10.c4 is appropriate, but it seems 10.dxc5 is playable, especially since black's KB is on d6