There’s diversity for sure. Old, rural, traditional Japanese homes are huge, most apartments are tiny, and standard single-family homes are usually somewhere in-between. The layout pictured here is most common in houses and apartments with multiple occupants; single-person apartments (especially cheaper or more modern ones) often have a more western-style “unit” bathroom with everything shoved into one room. But there’s a lot of variety; for instance some places have the sink and tub/shower together while the toilet is separate. Japanese homes (especially apartments) often only have one bathroom, so separating out the bath, toilet, and sink/vanity is actually a space-saving compromise, because one person can be using the toilet, one taking a bath, and another brushing their teeth all at the same time with relative privacy without the need for a second (or third) bathroom.