Yes, it is interesting. It is also good to be reminded that the upscale SAHM belongs to a tiny minority. The reality of most people is quite different.
We had an interesting discussion about this on mothertalkers where I am a featured writer- one of my co-writers who has a blog called Mombian about lesbian motherhood did an interesting job dissecting the data and noted how it completely disregarded same sex households where a partner stays home, which are actually very common -- I'll see if I can find what she wrote