I didn’t read the article, but I know you need to be careful with vit. D supplements. If you take too much, the body can’t utilize it all, and stores it in places that cause problems.
Calcium does produce harmful effects, but only if you get too much of it. If his diet has very little calcium in it he might be okay. And even if it doesn't, as long as the supplement has a 1:1 ratio, he should still be okay as it will even out the supply of calcium and magnesium in the body.