That's exactly what it means. It's called baker's percentage[1]. I find it useful for getting repeatable results when scaling a recipe.

[1] http://en.wikipedia.org/wiki/Baker_percentage

That's not what cognitive dissonance means.

0.5% salt by my calculation is still 2.6 teaspoons (10g) of salt - In 2L of water that does not seem insignificant. When written in terms of percentages it does.