Peeing in the tub is extra no when you consider that the Japanese are often recycling that particular water across multiple family members since they're supposed to be clean by the time they get in there anyway. The outside the tub part they ask about here is more or less the same as a shower I guess though, with the bathroom design they're probably talking about here. Y'know, drain in the floor, showering to wash off out there, then you take a soak in the tub.