If you guys can see that your fish are stressed by your water change method, isn't that enough indication that the Python methods are seriously flawed?
If you were in a room were a canister of nerve gas and a canister of the antidote were released, would you remain in the room or would you get the hell out? Do you really think that having the antidote means that there will be no repercussions for exposure to any toxic substance?
Your fish can't get out but they are telling you that something is seriously wrong. Chlorine burns fish's gills, even for momentary exposure. There is no telling what kind of damage or pain is caused to the sensory pits or lateral line.
You owe it to your fish to take the time to do it right. Pretreat your water. I use a barrel and then pump it to my tanks. I have also instead used a carbon pre-filter in my lazy days, but you have to frequently test the water quality.