Facebook first introduced an Instagram app for Windows 10 back in 2016. The company's suite of apps used its own OSMeta cross-platform development tools. That's about to change though. As spotted by Aggiornamenti Lumia, it seems that the social media firm will be packaging up the Instagram web app for distribution on the Microsoft Store instead.
The change will have various benefits, such as a much lighter app that does little else than provide a WebView that points to the Instagram web app. It's also easier for Facebook to maintain. Any updates that happen on the server-side automatically happen in the app. There's no need to maintain a separate branch of support like one would normally have to do for individual apps.
The app would seem to be a hosted web app, rather than a progressive web app. In fact, it's pretty easy to tell if a website is a PWA by if Microsoft's Edge browser offers an installation button in the URL bar, something that you won't see at Instagram.com.
Either way, it's likely that Instagram users will see better support on Windows 10. Previously, the app was not updated very often.