Jamair,
If I'm not mistaken Cessna checklists for the 182 actually call for fuel to be selected to the right tank when shutting down the aircraft. The reason is that when selected "OFF" both tanks are still connected together by the same port which allows selecting "BOTH" tanks as the fuel source. This will allow fuel to flwo from one tank to the other if the aircraft is not level and out the tank vent. By selecting the right tank there is no connection between tanks so flow cannot occur from one tank to the other.
Just dug out the manuals and the 182Q manual does state select right tank as the last item under "securing aircraft" on the checklist.
The 172P manual makes no reference to turning the fuel off as part of securing the aircraft and it's possible the 150/152 is the same which would explain why these aircraft spent so much time in the "BOTH" setting