I've heard it said (on this forum) that DMS is a non-issue for extract brewers, too, but don't recall seeing any data to back it up, nor do I fully understand the chemical reaction that results in the formation of DMS.
All I know is that it is formed in the boil and evaporates. Malt extracts (at least the *liquid* form) are 'boiled', so I can see why the DMS MIGHT be removed already. But, then again.... they 'boil' the LME during manufacturing a vacuum and at much lower temperatures than the boil you would get in your kettle, so.....
Ground Fault Brewing Co.