1) I wouldn't say it's normal or abnormal (see point 2 below). Hamstrings are one of the main loaded muscles groups for both the cleans and squats, so it's not necessarily an indicator of bad form.
2) Soreness can result from anything you're not acclimated to: load, volume, and/or the specific activity. "First cleans" means it's not a drill you're used to. The total load for double cleans is typically higher (often significantly higher) than for one-arm swings. So even though cleans and swing overlap a lot, the groove is not the same, and if the load is higher that makes two reasons S&S might not have acclimated you. Plus, on DFW you're also doing a lot of squats, so if you're not used to that, that's another factor that might lead to soreness.
3) I've never run DFW with the specific goal of fat loss. I just look at it as a C&P and FSQ program. Depending on how you eat, I think it could lend itself to different body composition goals. It's based on accumulating volume and increasing density with a relatively heavy weight (at least for the presses), and that can definitely be a recipe for hypertrophy.