Are you really trying to argue by implication that the Impreza is based on the "Impreza" WRX STi? All because you read Petter(along with plenty of others) saw an advantage to racing a hatch versus a sedan? Solberg doesn't make production decisions. I don't care what anybody says.
Despite what the commercials want you to believe... comparing the WRC car to what we buy at the dealer is practically like comparing the old Nascar cars to what people bought at the dealers. Of course some production decisions may be rooted in knowledge that was gained in racing but I'm afraid that does NOT mean that the Impreza is "based" on the STi. No matter how bad some want to believe it.
I drank Tang with my breakfast as a kid. Tang was used in space flight for astronauts. No matter how much I may have tried to convince myself of it when I was 7, my eating breakfast was NOT based on the space program.