Even though Google is an internationally acting company, the Play Store has always been a pretty local experience. Many apps aren't available in every location, and in order to not populate the Store with apps that aren't even accessible, Google hides results and items you can't download in the first place by default. On individual developers' app listings, this is bound to change, as Google has started showing every app there regardless of availability.
Left: Specifying that Instagram Light isn't available in the US. Right: Instagram's developer listing now includes Instagram Light, too.
The revised app listings first popped up last month and were rolled back again, leading us to believe this change was a bug at first. However, they've returned this month. A Googler confirmed to us that this is in fact working as expected, so it should stick. The new listings are available on both mobile and desktop, though the mobile version is more precise: The Play Store app will tell you an item isn't available in your country while the website just says none of your devices are compatible with an app, which is quite inaccurate.
The Play Store website isn't as straightforward as the app and just claims an item isn't compatible with your devices.
You can check for yourself by heading to Instagram's or Facebook's developer listings. A couple of apps there aren't available to users in the US and much of Europe, such as Instagram Lite or Free Basics, which are both tailored to developing markets.
Note that unavailable apps won't pollute your search results – they'll only show up on developers' listings. Google's reasoning behind this isn't clear, but it'll sure make our job here at Android Police easier. We often have to cover apps that aren't available in our countries, so having them neatly listed on the developer's page without resorting to a VPN or other tricky methods helps out a lot.