Pokémon Sleep just rolled out version 3.4.1 with a small but useful change ahead of New Moon Day #13. The update makes it so Pokémon with boosted special appearance rates can now show up in every area during the event instead of being limited to certain locations. It is a nice quality-of-life tweak that should make the event feel more flexible for players who prefer sticking to their favorite research spots. The update is live now, so players can download it before the next New Moon Day begins and start planning their sleep sessions accordingly.
Source: Official Pokémon Sleep news