Heyo! Glad you had fun with it, and thanks for coming back around after your first try early on ahaha.
The spermy flag doesn't really have much function in the demo. It essentially flags that they are impregnated. (It's usually gotten from doing their endurance mode). It will likely just effect endings.
If it is grey with an "X" through it, it means you cannot get the icon at all. Samga1 is crossed off because it is achieved from Samga2. Faye is crossed out simply because she has no endurance mode.
If there is no icon then it means you are able to get it, but you have not gotten it yet.
I do want to rework the indicators in a future update as I do agree it's unclear.