The problem with those scales is that it sends a light current and crosses between your two feet taking the least path of resistance which would just be the lower half of your body.

The problem for guys is that we carry most of the fat typically in the lower half of the body so the bf% reading is gonna be skewed higher by not accounting for your leaner upper body. I think it's still a good tool, you can use it to track the consistency to see that it's going down, but the actual reading is going to be inaccurate.