I honestly don't know if there is that much point in doing something like this. It seems to me that it's better to leave the store as it is without any quirks.
Thanks for your efforts in finding this. Although I don't know how much I or Frafro will be guided by it. Well in this mod I intend to mostly introduce something of my own rather than follow the ideas of the original creators.
What do you mean by that specifically?
In Shory this is done in such a way that after the sex animation Spider sets a global variable with the id of the player he has inseminated and sets, and also variable with egg. Then the updated.c script, which refreshes non-stop, checks if such a variable is active, and if so, it runs its script. This script create a local variable named Time, then, if it exists, it adds +1 to it and retrieves the value of Time once again. At the end if the Time value reaches a specific value then all global and local variables are removed, and a birth animation is forced on the player.
Here the script used for this Timer: