I think you hit the head on the nail about the showers. It is in a way the ultimate marking of territory. For submissive, it is I care for you so much I want you to mark me, or conversely, if consumption is desired it was I desire you so much I want all of your essence in me.
The other thought that hit my head while reading this from your POV, it is also saying.
I know I have heard women have to pee after sex, and I want you to be so relaxed that you feel no discomfort. Release and be happy.
Great share .... and great observations!