I can't answer why the dry hopping of a lager gives grassiness, except that these beers are so clean anything shows up as off flavors without much to cover it up. Dry hop in a sock for 5 days during lagering. You don't need much, it's not an IPA, just an extra touch of aroma. So I guess later would be better as aroma fleets. It would be easy to overdo, so I'd take samples.
Someone must have dry hopped a Pilsner/Lager/Kolsch successfully and written about it.[/QUOTE]
I think someone has, but perhaps the flavor profile of a pils is somclean that yes everything shows. It could just be the saaz hops that make those flavors, so a different kind of hops could change things.