For pots with drainage holes in, yes I add pottery crocks - saves the compost falling out of the bottom. It also will help drainage if your pot is sitting on a flat surface, to the extent that the roots won't be sitting in a puddle.
For large containers, I fill the bottom with gravel, partly for drainage and partly to save on how much compost is needed. Also adds some weight. I've tried the polystyrene bits but when I put the soil in the polystuff floats
Also what happens when you have finished and need to empty the pot back on the soil, or into the compost heap?
Anyway, old wives have had many good ideas over the years, accumulating far more knowledge than any baby-faced research worker thinks he knows