I think Schnarch is trying to say that perhaps females feel the same way (sometimes). After she has had hers then maybe she doesn't have anything left to give. Perhaps she might enjoy allowing her man to go first and then take her time afterwards knowing she just can enjoy herself.I haven't read the book, but I would disagree that the male is selfish to make sure the woman is taken care of first. I consider myself to be a very generous lover, but after my own orgasm there just isn't anything left in the tank until I've recovered for a bit(snuggling and afterglow yes, but going down on my wife will have to wait for a few minutes). In fact I think it's very unselfish of the man to make sure his wife/gf has been well taken care of first. I'd be curious to hear from women on this. Maybe Schnarch is suggesting it's a female empowerment thing? Doesn't really make sense to me.
Admitting you have nothing left to give after you get yours, I think Schnarch is making it a point to say oral does NOT have that limitation.