Why the Replicant Blade Runner “KD6-3.7” has the natural born female replicant Stelline’s wooden horse memory –
I can only speculate, but after watching the movie several times and reading some other very good theories, I have made some observations and formulated my best guess.
No replicant or human thought to ask Stelline if a memory is real or not. How would anyone know anyway without going inside her mind? The memory of an orphan is hardly copyrighted material or terribly significant. A law like that in a dystopian, corrupted society especially is most likely sort of a copyright infringement clause to keep you from copying an actual human mind into a replicant, making them too much like a certain real person, etc.
Stelline seemed pretty glib about it when K asked about using real memories. They have memories manufactured on purpose, otherwise they could just download a bunch of memories from books, movies, etc. Then you would have a replicant with memories of running through a cave with a giant rolling ball chasing him, swinging from a whip, etc. Now you’re risking a lawsuit from the estate of Stephen Spielberg, etc.
Putting one of her childhood memories in with everything is else is probably a minor thing. Very likely many replicants designed by Stelline have that memory. Especially ones who are designed to be subservient protectors – Blade Runner, etc. It evokes feelings of powerlessness, but also of protecting something special. It’s a powerful one for Stelline.
It symbolizes her father and perhaps sharing that memory with replicants is her way of sharing her sense of loss, her own loneliness. Regarding how she got where she is - I theorize she was most likely briefly adopted from the orphanage by wealthy human parents but when she developed the immune syndrome they abandoned her on earth. That all could very likely be true, therefore she has no idea she is a replicant.
She has know way of knowing K found the horse and thinks he is the natural born replicant. He just misunderstood the whole thing.
Imagine though, if you wanted to start a revolution, which in the movie is apparently coming. (Sequel?) What if the figurehead of the revolution was someone you share memories with? Some one who helped form you and make who you are? That would be a powerful leader.