12% body fat with enough muscle to almost be considered obese by BMI standards is quite a few standard deviations outside of the mean. Anyone with that kind of body is well aware of that BMI shortcoming. For most of the population, it’s still a pretty good rule of thumb.

There's a very good chance you're not testing your body fat correctly. I've gotten several friends, including bodybuilders and various athletes to get DXA scans done... pretty much every one underestimated their BF% by 5-10%. Including the ones who swore up and down by their personal trainer's caliper measurements, the BF testing machine (the electric handles one) at their local supplement store, etc.

I'm 14% BF and a BMI of 20... looks to be right on point.