When I saw Whitesnake back in...has to be seven or eight years ago (it was when Priest was doing the anniversary of British Steel tour), I saw a local festival with Whitesnake, Priest, and Tesla. First and only time seeing Whitesnake. Coverdale has exactly the same issue live that Joe Elliott of Def Leppard does. His lower voice is there, and he can do falsetto to cover the fact his natural high voice is gone, but his mid-range is non-existent. It was weird. Obviously, in-studio, they figure it out, because he can sing the same line a gazillion times to get it. But live, that's the drawback of Coverdale these days. His mid-range, and primary vocal, is shot. So they lower the key so he can sing it lower, and have the other guys fill it all in with the mid-range and highs. Lepp's been doing it for 20 years now.
Is what it is. I have no desire to see Whitesnake or Lepp again, but both put on great shows, despite the singer limitations.