Pace, how many PPL conversions/checkouts have you done?
I have trained pilots up for a Citation SIC ratings and signed them off and sat in with numerous PPLs on a variety of singles and piston twins.
But as stated have literally years back had the keys thrown at me on complex singles I have never flown and got on with it.
Some time with the POH, Some time sitting static in the aircraft examining every switch and then flown off sometimes into IMC with such aircraft.
Its no big deal and I am nothing special
I really do think its either money making by the training establishments or there are some pretty incompetent pilots around.
As for a PPL yes PPL going from a PA28 TO c152 ???
its a bit like driving a ford fiesta and needing instruction to drive a volkswagen polo. Your not going from a ford Fiesta to a formula 1 Car.
Pace