For what it's worth I'm on hctz (diuretic) for blood pressure - admittedly lower end dose but always on it. I've run dnp a number of times with hctz. Anywhere from 250eod to 500ed. Zero hydration issues for me. No cramps, no dark piss, nada.
As with most things it's down to details, dosages and individual. Similarly many of us have have violated bro science gospel and ran Anadrol over 4 weeks and not needed a liver transplant (actually many here including myself have shown in range liver values). Just citing a similar bro science unfounded example.
What's happened is tragic and sad. Completely unexpected to have someone otherwise healthy suddenly taken from family and friends. However I'd caution against trying to extrapolate a simplistic binary life/death lesson here.