I don't think it's too much reaching to say some of the leaks are intentional. Hasbro has been proven to leak things intentionally and then proceed to make changes according to how people react. I just think it's smart. Pandering, perhaps. But isn't that kind of what you need to do to make sales?
I don't believe ALL leaks are intentional. How they happen is anyone's guess. There was a 4chan thread about a translator hinting at new Pokémon and a new region and all that stuff and that I understand, obviously translators are a "danger spot" for leaks. But when things like screenshots of the game (supposedly) and official character reference art leaks (that actually happened) we have a bigger stew in the pot that I'm finding a hard time to explain.
While I have the controversial opinion of liking more cutscenes in the games, I highly dislike the random small cutscenes that break you out of getting from place A to place B, like the Nosepass/Delibird thing. I really wish I could witness things happen automatically rather than to have to activate them myself, you know? Like birds flying above me when I run through a route. That's cool and makes the world feel living. Maybe have birds land on the ground picking for food or something and take off when you get close, or have a poochyena jump into a bush to hide from you when it sees you coming, or just have random wild pokemon interact with each other, ~WITHOUT ACTIVATING A CUTSCENE.~ I LOVED seeing the Bewear walking about near the Battle Tree, and Magmar near that...um. Mountain. Thing. Please. More of that. Moooooooooore.
Also, agreed. Don't lead people on. If I need to come back for the Vulpix, give it to me in the end what did I do this for