How new Regional Forms could be explained in Legends Z-A

A lot of people are questioning whether or not we will see any new regional forms in Legends Z-A and I believe that we will see at least a handful of new regionals.

First off, we don’t know how long it takes for Pokemon species to change and adapt to their environments. In Legends Arceus it’s stated that the group of starters that you choose from came with Professor Laventon from another region, which would make those 3 Pokemon not native to Hisui yet all 3 of them evolve into Hisuian forms. This means that all it can take for a Pokemon to evolve into a different form is by simply changing the environment that a Pokemon grows up in. Though I believe that the 3 Hisui starters were caught in Hisui, taken to another region to be studied, and then brought back.

Now onto my actual theory!

The easiest way to explain the sudden form change of multiple species of Pokemon would be to say that they changed so fast because of the firing of the Ultimate Weapon during the events of X & Y. They could say that the residual energy left over causes these Pokemon to change faster than normal into new regional forms!!!

What are your thoughts on this theory and how do you think they could explain new regionals if they were to explain it?