re:
Diffuse and receeding involve the same factors, the miniturization of hair follicles through the action of DHT. Many only experience this thinning and eventual follicle destruction in the front because those follicle have been recognized as the most "sensitive" to DHT. This is the reason why Merck and rogain do not claim to help for frontal hairloss, not because these treatments will not at least improve or slow down frontal recesion, but because these follicles are just too prone to destruction and the companies do not want their product discredited. Most experts agree that finasteride and minoxidil will improve frontal loss, but the distributors clearly state that it does not.
Women have no set pattern for hairloss though they do "tend" to have thinning all over.
The exact reason why one person just receeds and another has thinning all over are unknown. However, you will notice that diffuse thinners tend to thin everywhere but their thinnest areas are usually their hairline and crown. You will also notice that receeders tend to start to lose hair in their crown as time goes by and eventually the crown and frontall losses begin to meet in the middle it just takes a lot more time then thinners.
Therefor, there is no real difference between a thinner and a receeder aside from the fact that the thinner simply has more follicles that are sensitive to DHT.
I would point out that I am no doctor and my comments are based on my own research and understanding of your question.