I brewed a Gose about a month ago. It was the first time I had brewed with bugs, and what I did was mash, boil for fifteen minutes, chill down to ~110°, siphon into a carboy and pitch a lacto culture for about 48 hours. Mine smelled awful when I siphoned back into the brew kettle after a couple days, but after a 90-minute boil it was fine. Based on my experience, my guess is that what you're smelling is indeed DMS. I'm no sour beer expert, but I don't believe lacto by itself should give any funk.