Other mistake: It is established in the movie that whenever Joi is switched on through the emanator, or when she tries to communicate with K when switched off, a chorus line from the song Peter and the Wolf will play. This is shown at numerous points: when K first activates the emanator, when K is talking with Luv at Wallace Corporation, when K is talking with the hooker, when K switches her on when he is analysing the DNA, when she is reset after the car is shot down and when she switches herself on to tell the hooker to leave the apartment. However, when Luv is beating up K, Joi switches herself on to tell Luv to stop, but the chorus line from Peter and the Wolf is not heard, despite being heard every other time in the movie. (02:00:30)
Other mistake: When K is shooting at the car Luv and Deckard are in, in the shot of Luv gasping and sparks flying due to the car being shot at, the co-pilot sitting on the right is shot in the head. The bullets that hit the co-pilot come in through the front windshield and the frame of the car beside it, as shown by the bullet holes made in the windshield and frame, and hit him in the side of the head. A blood splatter from where the co-pilot was shot can be seen on the windshield, but the angle of where the bullet comes in through the windshield and hits him on the head doesn't match where the blood splatters. The bullet comes in from the front of the car, hitting him on the front side of the head, but the blood splatter is seen on the windshield directly in front of him. If he has hit in the front side of the head, the blood splatter would come out through the back side of his head, and not hit the windshield. The only way the blood splatter going on the windshield could have been possible was if he was shot through the back of the head, and not through the side of the head. (02:19:55)
Other mistake: When K intercepts Luv's car at the sea wall to rescue Deckard, the two begin shooting at each other, and end up hitting one another. Luv then falls onto a car seat and a huge splatter of blood is left on the seat, but there is no visible wound that can be seen on her that would have been able to produce that amount of blood splatter. (02:21:55)
Other mistake: In the trailing credits, the 2nd song, "Cloud" references the word "preformed" rather than "performed". (02:41:40)
Answer: Think of any manufacturing process. Samples of new products are frequently created and then immediately destroyed. Also, the new replicant would require processing, training, etc. It was simpler for him to just dispose of the test.