The vast majority of people live in, and the vast majority of economic activity takes place in, major urban areas. So yeah, housing inflation is very relevant.
And all of those sales are included in the link I provided, which shows that housing has gone up 13% nationwide since the peak twelve years ago.
considering the fact that in all metro areas housing prices have almost doubled, I'm curious in which parts of the country the housing prices decreased by half to reach the 13% average increase
Washington DC has for one not doubled. I'm not sure you're statement is accurate.
Housing going up 13% means most homeowners made over 60% return on their money.
There are plenty of urban areas that haven't seen drastic increases in home prices.
Some have even seen a decrease. Chicago has just made it back to peak 2008 level: