As I understand it, the A320 had this kit when it first flew in 1987. Boeing had the chance, when they completely re-engineered the 737, in (I'm approximating) around 1997 for the 737NG, and again around 2015 for the 737Max. They didn't. A drop dead date was then set for 2023 for this to finally be there, and that is only for type certification, not for service or withdrawal date. They haven't meet any of that either. Talk about bending over backwards to help Boeing. But they just don't help themselves.