>>30221663>Even if Wally catches a shiny Ralts (and he can), it turns non-Shiny once he gets it.That is purely because of how Trainers are defined in the game code.
For example, the many times you battle your rivals? They're not actually the same trainers. They just appear that way. Each time you battle them they could have completely different natures/IVs from each other unless specifically coded to stay the same (which, at least in the older games, isn't the case).