The PCM controls air conditioning clutch engagement and the 12B37 update did change the PCM software a bit, but neither our SE with the manual a/c or our SEL with the DATC have exhibited this issue since the update back in May. They both start cooling within a minute or two of start.
My first question would be whether or not the clutch is engaging on start up or not engaging until the car is in gear.
As suss6052 points out, the vapor cycle air conditioning system relies on cooling air flowing across the condensor to cool the refrigerant. Even once the clutch is engaged, it takes time for the system to work up to operating pressure and for the cooling cycle to reach a point where you'd notice the difference at the vents. I know that on both of our cars, it takes considerably longer to feel the difference on a hot day.