It used to be more true, when straight chlorine was what was used. Now most municipalities use chloramine, which is more stable. Most plants don’t care, but it’s an issue for fish, so there are “water conditioner” products for aquariums that remove both chlorine and chloramine.
I think it’s likely really surprising to learn/experience that feces of a breastfed baby (and to a lesser extent formula fed babies) don’t smell like shit. It’s natural to want to share a surprising learning. Might also be good to be forewarned the milky smell ends once normal food is introduced.