Trash bytes & Hidden Abilities on Gen7

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Hey there!

I have been considering to change a Pokémon's ability to its hidden counterpart. If I remember correctly, I had to edit the extra-bytes in order to make it legal.
On my first try, I just changed the ability without editing the extra-bytes, and the program says it is legal.

And then, I randomly edited the Pokémon's and it's still legal,  extra-bytes Do extra-bytes matter at all?
Is editing the extra-bytes for hidden abilities still necessary? Or is this automatic whenever I choose a hidden ability?

Thank you!

[Kaphotics]

PKHeX edits the dream world ability flag for gen5 format files automatically, no need to modify extra-bytes.

The extra-bytes are just a holdover to expose all bytes for editing, even if they are unused.