Having more melanin decreases the effective dose because any photon that melanin absorbs isn't going to be absorbed by your DNA.
Primary institute of skin cancer in Australia: https://www.cancer.org.au/cancer-information/causes-and-prev...
See number 2.
I'm hypothesising you may live in a place where skin cancer is not a big issue?
Having more melanin decreases the effective dose because any photon that melanin absorbs isn't going to be absorbed by your DNA.