I do a lot of light German lagers and employ a very similar procedure using a CFC instead of a plate chiller. I recirculate and whirlpool through the chiller beginning at flame out (was having problems with the boiling wort and March pump cavitating and decided I would get enough kill power with just under boiling water). Depending on whether I add flame out hops, I will whirlpool for 10 to 15 minutes before I start running water through the CFC. Once I have it cooled down as far as I can get it to go on hose water (well below 140), I let it sit for 10 minutes to settle, then knock out.
Never a discernible amount of DMS in the beer.