>>37290373Probably because the writer of ORAS was only hired for that game and already quit Game Freak, he was only in SM credits for the dex entries he wrote in XY and found him in LinkedIn looking for a job.
And Emerald maybe because it didn't sell a lot.
Actually, USUM sold poorly too so I feel like I can't predict if GF would choose to represent SM or USUM elements in future games or try to mix them both.
Also I feel like the changes of the USUM scenario were more directors and producers preassuring to respond to fan demands than the series writer just changing it because of reasons, they brought up people who cried over Lillie.