Along with Mo and HH, Isaam mentions the treasure (whether directly, I don't remember... he DID say that "every cave has at least one pearl") and I think maybe one other pedestrian does...
Citation:
Après, c'est difficile de croire qu'il n'existe sur la planète entière, que cette petite partie explorable que nous avons pour jouer. D'autres villages, d'autres pays, etc?
I don't think Hillys is very big to begin with— I think the city and the outskirts make up what's been built. Hillys is the name of the planet, but is it also the name of the city? The city's name is never mentioned... I guess it wouldn't need a name if that's all the planet has to offer
Besides, the smaller the area, the easier it is to keep people in!
The Yo Pearl! disc in-story could just to kind of repay Jade for her continued support of the garage (not really worth it).
Nevermind pearls, what about the animals? "All species", is hard to believe. But some official texts say you have to photograph "what they don't already have". (no human photos tho?)