Is there something special about bubbly water?
You're basing this question on an incorrect answer. Like you said, the boiling temperature of water is lower at higher altitudes, which means it takes longer to cook things in boiling water, due to the lower temperature. There's no benefit that I'm aware of in intentionally lowering the boiling point of water (which a pinch of salt does not do, anyway). If you wanted to cook something in water at a lower temperature, you can always just use less heat to keep it below the boiling point.

Put another way, water that is boiling at 190&deg;F does not cook food at the same rate that water boiling at 212&deg;F does, even though they are both boiling.