Yesterday, Microsoft announced that it's previewing a brand new version of Microsoft Launcher for Android. The new app is built on a new codebase, which adds features like landscape mode, and it also has a lot of UI tweaks compared to the current stable release.
The new app is still in early stages of development, which might be why Microsoft decided to separate it from the current beta program on the existing Play Store listing. And maybe it's because of that that Microsoft is also distributing updates to the new Microsoft Launcher preview program in a different way. While you can get the app from the Play Store, updates are being released frequently on Microsoft's App Center, as spotted by Twitter user Kris Petrin.
The best way to get these updates is to check for updates through Microsoft Launcher itself. Head into the Launcher's settings, then choose "About Microsoft Launcher". From there, you can check for updates, which will take you to the download page - which you can also visit here - if there's a new version. Note that the ability to check for updates has always been built into Microsoft Launcher, but it would just take you to the Play Store, so most people might just look for updates there. Now, there's a good reason to use the built-in update checker.
It's likely that Microsoft will still deliver updates through the Play Store, but the company might choose to only release larger updates through that platform. If you want to get the latest bits on a more frequent basis, you'll want to check for updates from inside the Launcher itself.