You are right. Anyone can diagnose anything(NP, PA, DO, MD, DC, DPM, OD, DPT, ect)
My point is scope for any degree does not limit the ability of the practitioner to diagnose only to treat. That being said legal a DO and MD has an unlimited scope but as we have discussed earlier this is not really true. They treat what they have been trained. A urologist opens himself/herself up for litigation if he/she treats a patient for a bunion or for brain cancer.