I agree it's confusing. I think they do it to remove seasonality and the experts on the topic probably don't understand anymore why the rest of us think their way of reporting is confusing to lay people.
Seasonally adjusted != multiply by 12. Prices naturally fluctuate throughout the year due to weather, consumer patterns, and business cycles. Seasonal adjustment is an attempt to account for those changes.
I agree the annualizing the monthly figure would be handy, as an additional figure. Looking at annualized monthly figures, it was also apparent (say) six months ago, that the monthly annual figures would almost certainly continue to get worse.