The extras are not supposed to be something you're "forced to read" at all - in fact, if an extra is actually interesting enough to stand on its own, I post it separately as a one-shot. Heard of J.K. Rowling's "Quidditch Through the Ages" and "Fantastic Beasts and Where to Find Them"? Well, think of the extras as that kind of thing. They're not something you have to read and don't contain any important information that you can't access otherwise. They're just fun things to read if you're curious about how people can teach Pokémon speech in chapter 3, or about where exactly the "never catch an unconscious Pokémon" rule comes from. Just to make that clear, there are NOT many extras in this fic. The next extra will most likely be after chapter 7, and then (unless I add in an extra that wasn't there in the revision before this one) there is just one for chapter 27. So basically, they're not exactly disturbing your reading after every other chapter. They're just a sort of "by the way, if you're curious about that..." thing - entirely optional to read, but as you said, they add some more depth if you do read them.
I see, that's cool. I might do that in a later story of my own.