I have heard this for years and it isn't so.
It isn't so where I live either and I have a red clay to clay loam soil.
You need to add 50% sand to the clay but I guess a PHD from Washington State University doesn't know what they are talking about.
http://www.google.com/url?sa=t&rct=j...,d.b2I&cad=rja
As for the furrows it is the very best thing you can do.
People in the gulf area of Texas do it all the time to keep the plants out of the water.
They have great gardens in their black gumbo soil.
Worth