Of course I'm not one to be able to critique Seirawan, but I don't agree with his advice. It breaks sereval principles, and doesn't gain much in return. First, it doubles pawns and captures toward the outside, reducing your number of central pawns. These are generally accepted strategic guidelines. Second, it blocks your bishop, so in order to make your fianchetto useful again, you'll have to move the pawn to f4.
There are a few gains I can see, but none of them seem worthwhile. It does create an open file. But most people would prefer having two central pawns to the open file. It also keeps the knight off of e4. But this can be accomplished in other ways, and it alone doesn't seem to outweigh all of the strategic guidelines that are broken.