Is my mom right that archery may be natural to me?

Of course anything is possible. I don’t think a nerf bow is an accurate comparison to a bow for hunting, though, if that is what you were thinking.

I enjoy primitive archery (more Robin Hood, less Darryl Dixon).

Using two fingers on a 40lb pull bow is a good way to injure yourself. It’s also harder to aim, because you’re using the index and middle fingers to stabilize the arrow as well as actually drawing back the string. Having the third finger takes a load of pressure off those two fingers and gives you some time to actually focus on a target before releasing.