The diminished heart attacts or cardiovascular disease is if you are drinking chlorinated water. The calcium/magnesium acts as a buffer to heavy metal and chlorine damage to the arteries and body.
There is no data that shows hard water is better for you than soft water. Even hospitals give you distilled water when you are really sick, and that is dead water.
Water is not the source of minerals. If it were it would be consistent, like vegetable mineral content proportionally. Water has whatever it dissolves, whatever it flows through.