Bottled water does NOT have all minerals removed, that would be distilled water. Never the less, water alone, just H2O, hydrates. That is what it does.
Electrolytes may need to be replenished, or not, but they can come from food. I defy you to survive on powdered GatorAide for 2 days, without water.
It’s about the EU saying water will not hydrate you. Nothing said about food. EMT’s do not give dehydrated people plain water. They use a hydration pack that’s high in electrolytes. Plain ater does not have that.