It's actually more complicated. There are thousands of potential compounds in a bottle of whiskey that come from both the distillation and ageing process, and even some leached from the bottle itself.
Whiskey doesn't necessarily taste better with water. It simply tastes different with water. It also tastes different cold. Since every whiskey contains different amounts of different compounds, every whiskey requires a different variable of water and/or temperature. Some are really good by themselves.
Personally, I can't stand Johnny Walker neat, while I find Macallan ruined by water. Decide how you like it for yourself.
"even some leached from the bottle itself" - Intriguing, I've not heard that before said about glass. Do you have any more info on that? Or are you talking about a potential to oxidise in the bottle.
"First, the water condensed from the humid air causes mainly sodium to leach out of the glass" - Wow! I thought glass was kind of 'inert' with ethanol at least.
"Items made of lead glass may leach lead into the food and beverages contained. In a study performed at North Carolina State University, the amount of lead migration was measured for port wine stored in lead crystal decanters. After two days, lead levels were 89 µg/L (micrograms per liter). After four months, lead levels were between 2,000 and 5,000 µg/L. White wine doubled its lead content within an hour of storage and tripled it within four hours. Some brandy stored in lead crystal for over five years had lead levels around 20,000 µg/L. To put this into perspective, the U.S. Environmental Protection Agency's lead standard for drinking water is 15 µg/L = 0.015 parts per million. Citrus juices and other acidic drinks leach lead from crystal as effectively as alcoholic beverages. Under conditions of repeated use of the decanter, the lead leaching steeply decreases with increasing use. This finding is "consistent with ceramic chemistry theory, which predicts that leaching of lead from crystal is self-limiting exponentially as a function of increasing distance from the crystal-liquid interface." Lead leaching still occurs, but the quantity that leaches into a glass of wine or other beverage let stand for a few hours is much smaller than the quantity of lead consumed daily in ordinary diet."
"The California Department of Public Health lead advisory states, "children should never eat or drink out of leaded crystalware". Leaded crystal wineglasses and decanters are generally not considered to
pose a significant health risk, provided that these items are washed thoroughly before use, that beverages are not stored in these containers for more than a few hours, and provided that they are not used by
children."
Alkalis in the surface of the inside of the bottle can be leached by the alcohol, raising the pH enough that it actually attacks the glass. To avoid this most glass bottles are dealkalized before filling, but if water from a humid environment makes it into the bottle before filling it begins a process which leaches various compounds from the glass. But this would take a long time to occur in whiskey (vs Vodka/Gin, which are less acidic).
Oxidation is probably more affected by the sealing method than anything else. Corks also change the flavor of whiskey due to things like absorbing certain compounds depending on what they are made of or coated with.
Whiskey doesn't necessarily taste better with water. It simply tastes different with water. It also tastes different cold. Since every whiskey contains different amounts of different compounds, every whiskey requires a different variable of water and/or temperature. Some are really good by themselves.
Personally, I can't stand Johnny Walker neat, while I find Macallan ruined by water. Decide how you like it for yourself.