And if you count building supplies and groceries, it's north of 10. The numbers are cooked, and the rate of cooking is increasing.
To the extent building supplies increase rent (new housing is a small portion of overall housing, so 2x spikes up and down in one component's price doesn't drive rent up 2x in one year), it is reflected. Groceries are included in CPI.
They count housing through rent, to avoid speculative asset pricing stuff.