In reply to original post...
As a C206/210 pilot based in Maun, Botswana let me assure you that the practice you(kiwiblue) describe is NEVER used by the pilots flying here.
1. I don't know if you have ever flown a C206 at 3100 ft AMSL in temps around 45degrees out of short, rough, dirt strips at MAUW, but if you don't push Throttle/pitch all the way to the firewall you're gonna be a lovely fireball at the end of the strip!
2. Even with the throttle open all the way we only can muster 25MP! So its staying all the way in bro, for takeoff, cruise and descent.
3. After 500hrs hours in a 206 i have never seen the oil pressure reach the red line on takeoff.
4. The only thing that gets wound back after takeoff is the rpm for the reason (as someone mentioned) to stop the prop screaming at 2850.
Cheers