You're never supposed to cook with hot tap water. Even if lead is not a concern, there are other possible contaminants that can leech from plastic and copper pipes, or from the tank itself.
There's a lot that's not formally taught in the US. But I'm in the US and this is a thing. The blended faucets are fine. If it was set to hot or some blend with hot in it, you set it to cold and let it run for 1-3 seconds.
