This situation is the first problem he faced when he reincarnated. It isn't a strange situation because he is not the only unborn Supreme Beast in the same situation. The plant that he is attached to is in possession of thousands of other fruits similar to his.
This plant is in a large vat of transparent liquid and one can see the form of the fetal Supreme Beasts through the thin skin of the fruits. No one will look at this setup and think it is strange even though Supreme beasts ought to lay eggs. This is because something happened to the Supreme beasts that Gehaldirah wasn't aware of.
Supreme beasts are strong. The ability to have more than one divine ability has made them a terrifying force in the realm of high heaven. But even with their power and influence, most people haven't heard about them or seen one of them because they are too few in number.