CPTSD literally rewires your brain and "appears" in diagnostic tests as ADHD: lower arousal in prefrontal cortex, overactive amygdala causing fast emotional response, impacted hippocampus, dopamine disregulation, etc.

Stress changes the layout of your brain along with your body's chemical responses. With ADHD, genetics seem to play a larger role where you can lack the stressors and still end up with the same end result. I wouldn't be surprised that treatments would work across both CPTSD and ADHD.