Pokémon Anime Ash-Greninja Bond Phenomenon, Squishy and Z-2 Never Returning in the Journeys series? Why?

I know that an Ash-Greninja bond phenomenon, and Squishy and Z-2 of the two Zygarde appeared only in the XY series, but they never returned in the Journeys series, not even as in either cameo. An Ash-Greninja bond phenomenon wasn't in the flashback of its battle against Alain's Charizard, but was replaced with a regular Greninja form instead. So, why do you think that Squishy, Z-2 and an Ash-Greninja bond phenomenon was excluded the Journeys episode featuring Ash's formerly owned Greninja? Were they mentioned in this episode? Why? And what happened to Squishy and Z-2? Please let me know, thanks.