The bathroom is where you shower and bathe.
The dunny, bog, toilet, Water Closet, poofter's hangout, shithouse, John, can, out-house, loo, Gateway to Werribee, hotline to parliament are just places to have a shit.
it's coincidental that you have a dunny in yer bathroom; but I guess it can be hilarious letting go an arsetrembler while someone is in the tub.....