I suspect a lot caomes back to the design of caravans. There will be a desire on the part of the manufacturer to try and balance weights in the van, eg kitchen one side wardrobe the other. In addition if he/she is trying to put in a fixed bed then there may be restrictions on where the toilet compartment eventually goes. At the end of the day you decide the internal layout you want, and if necessary live with compromise outside. Many caravanners nowadays also prefer porch size awnings and here the issue does not arise. Also the Europeans are now putting the fixed bed and the toilet compartment towards the front of the van so maybe that will change things yet again.
I am sorry but life is too short to worry about these sorts of things. if you are really concerned, don't use the toilet, or buy another van. After all just think of using a European 'Turkish' toilet and be thankful.