The exact point of stating ‘What he said’ when what was said had already been said has yet to be fully determined (particularly when what was ‘said’ was perhaps neither true or accurate). It is often considered a phrase used by the inarticulate and confused.
Contributor 1: ‘White dog poo is the calcium left behind as the water evaporates, and the 'organic' components of the poop are consumed (in various ways) leaving the inorganic stuff behind. But nowadays dogs don't eat as much bone as they used to, including bone meal. Also, tighter regulation on dogs crapping on pavements means that turds don't hang around for years in public places like they used to, giving them less opportunity to dry out and turn white.’
Contributor 2: ‘What he said.’