God does not will a soul into existence and then wait around to find it a suitable body.
No one’s arguing for preexistence, but anyone who’s ever created anything will tell you that if the idea happens before it ever is physically manifested on a human level-- sometimes days, or months, or years, or decades before— how much more so would that be for God, who exists outside of time?
I can choose today to dye my hair purple. Now I’m a purple-haired American woman living in the 21st century— but being purple-haired isn’t an intrinsic part of my existence. It’s an attribute, but it doesn’t make me “me”. I’d take it a step further and say that I could have just as easily been “myself” if I hadn’t been born an American, or lived in this time and place, but this time and place were prepared for me to fit into it, like a puzzle piece. If I wasn’t here, there would be a gap in so many things.
My parents thought I might have had an elder sibling, but weren’t sure. It might have been a missed period, or it might have been a miscarriage— I never asked, and they never went into details. But if that person had existed, I would never have existed as “myself”— purple hair or not, American or not, 21st century or not.
If God had allowed that person to exist-- he wouldn’t have said, “Well, I guess there’s no need for Midori.” Instead, I would have existed… in another time or another place, with another family. And I still would have been “me”, but all the variables associated with my existence would have been different.