Your edit is very interesting and explains why my mother (who lived in the UK from 11-25) ingrained in me as a child to let the water run cold for a while after

Your edit is very interesting and explains why my mother (who lived in the UK from 11-25) ingrained in me as a child to let the water run cold for a while after switching from hot before drinking. She said it was due to increased rust in the longer hot water path, but I suspect that it is mostly culturally ingrained due to your explanation and the rust explanation is just working backwards