I agree with flaps approx 15 for a 182 to have a smooth "early nose lift off", but from experience prefer to use flaps 10 for 172 & 206 on short field T/O. I have the impression the nose and firewall at the 182 is comparably weakest for weight.
But, early nose up does increase drag, so you trade some short take off distance for the early nose up - which may be why Cessna did not write it in the POH. If you know exactly what you are doing and are absolutely sure ISA+T & DA are no issue for the runway you aim to take off, you may proceed on own discretion.
Most of the times, especially with the 182 T/O performance, you will have no problem to lift nose early, but be very careful in x-wind situation!
In the end, it stays a non-approved custom procedure!