No, this doesn’t seem to be typical video game oversight of leaving bathrooms out of video games. There is actual merit as to why the Davenport Manor is absent with a proper bath and toilet:
Many European colonists objected to the Native’s use of water for bathing and drinking.
According to European religious beliefs prior to the time of the Crusades, bathing with water was considered an act of temptation causing sexual arousal. As a result, bathing was outlawed in many areas of Europe. When European colonists arrived in America and saw the Native Americans openly bathing with water, they objected to the practice and pronounced the Native Americans “heathens.” The importance of bathing for hygienic purposes was foreign to Europeans until crusading soldiers, returning from the Middle East, adopted the idea of the public bath. However, use of public baths was not widespread; to the contrary, it was reserved for the elite, who were few in number.
Source: [x]
So for all of you perverts out there that fantasize about Connor bathing butt-naked in that lake not too far from the manor…welp, you’ve had it right all along.