You're quite right, Scott.
Running water will for most praktical purposes use more than 10 times the CLEAN water one uses by changing water X times in the tank. Since about 7 changes plus a little time is all that is really nevessary (se previous post with a simple calculus), its easy to see that changing water merely uses a gallon or a little more than that, while running water quickly uses 10 gallons or considerably more.
Since we're rinsing out chemicals, everyone must understand that the pollution argument is non-valid, both methods aims to put the same chemicals in the water. One method dumps them quickly, the other slowly, but that is inconcequental, this amount of now unclean water very quickly dissipates and mixes with enormous amount of unclean seewage.
In large parts of the world clean water is more valuable than oil...... so use it sparingly!