Because it is tap water, cold water contains heavy metals, microorganisms and other chemicals, which are harmful to the body, so it is reasonable to advocate boiling water before drinking.
The number of microorganisms in boiling water is greatly reduced, but it is not absolutely absent. In addition, heavy metals and some chemicals react at high temperature to produce insoluble substances, which can also remove these harmful substances to some extent.
Therefore, some doctors suggested that tap water should be boiled before drinking. If it is not boiled, don't use it, which is harmful to your health.
So if by "cold water" you mean boiled water, then this drinking method is obviously the same as drinking boiled warm water.
If you mean "cold boiled water", it's not a big problem to mix it with hot boiled water.