You are assuming a molecule good at shielding against UV light is probably a poor shield against gamma rays, many orders of magnitude shorter wavelength. That sounds probable ...

But how about the theory that systems to clean up smashed up proteins from UV light is also good to clean up smashed up proteins from gamma radiation?

And one of the parts of that system, or upregulated with that system, is melanin.

That makes me wonder if Ayam Cemani chicken have better tolerance to radiation than other breeds. See https://en.wikipedia.org/wiki/Ayam_Cemani