Yes, but people don't wash their hands between wipes, and there's a chance that poo contamination could go on the wall.
I'd rather people's potentially shitty hands don't smear on my wall, or indeed any wall, thank-you.
Anyway, the germane point is this: those in favour of method B have given a logical and reasonable answer as to why this should be the case, those in favour of method A have not.