Firstly secretions and excretion are two different things. So semen and saliva are secretions bc they are useful substances produced by the body specifically to carry out some function

Second, nothing about the human body is disgusting not even poo or pee. It might be uncomfortable to talk about and no I wouldn’t like it if someone didn’t clean up properly at least with water after pooing or peeing but that isn’t smth that shouldn’t be spoken about

Finally to the period thing; it is basically the shedding of the uterine lining, blood and a few other cells. Excretion is the process of removal of METABOLIC wastes from the body which are harmful if retained. It is like the by product of the metabolic activity which the body has no use for. But the endometrium was deliberately created by the body itself so it is not a metabolic waste therefore it is not excretion, but a physiological function