Marc, all I can say is that goes back to the writings of the early and mid 1970's, by people who knew no better. Interesting
it is being perpetuated today, when we do know better. Like the bore butter concoctions, perhaps it does build up inside the
bore, contrary to their statements and the scalding-hot water is needed to melt it to remove it.
I use cold water straight from the tap - works just as H&H (long time gun makers of England) stated it would. They also stated
that VERY hot water will have a caking effect on BP deposits (breech face) instead of dissolving those deposits like cold water does.
Does cold water actually dissolve powder fouling off the breech face? - dang right it does.