Nomorecatering
Yes, do agree with your sentiments regarding cool down happening during the approach. Also agree with once you are on blocks, unless facing into wind on an ISA or colder day, the CHT's will often go up a touch.
I believe if you were able to jump out straight out after shut-down and take the cowls off to aid cooling, this could still cause problems with turbo's. The reason for the cool down is primarily to enable oil moving around the turbo to take the residual heat way. For even cooling of the turbo, the movement of oil at a low power setting does this best.
If the CHT rises a touch during this process - so be it.