A quote from that link
The Mini is, aerodynamically speaking, a housebrick. When a car is this square it takes a heap of extra power to lift the terminal velocity, and Brodie’s boys deserve more than a pat on the back for squeezing 160mph, just 40 less than a Ferrai Enzo, from a shopping wagon that carves the air like a nailfile cuts sheet steel.
it may be a brick and its Cd may be high, but its frontal area is small so the actual drag is not bad.