I’ve read the same about BMI and center of gravity making it difficult for some colored people to float and even swim.
I’ve seen it with my own eyes. I’ve held people (one hand on the small of the back) up in the water and verbally walked them through all the steps (1. arms over the head, 2. fingertips out of the water, 3. knees bent 90 degrees, 4. maximum amount of air in lungs, and 5. holding breath). Some people can’t float.