AdDuplex released its monthly report today, showing Windows usage based on usage of apps that run the AdDuplex SDK v2 or higher on the date of June 26. AdDuplex runs on over 5,000 Microsoft Store apps.
Only 6.3% of Windows 10 users are on the latest version, the May 2019 Update. This actually isn't very surprising news, and while the rollout timing is similar to 1809, it's for a completely different reason. The Windows 10 October 2018 Update had a bunch of issues that caused it to get pulled from Windows Update servers, and it never really gained traction after that.
As part of preventing things like that from happening again, Microsoft won't be pushing feature updates on users and forcing them to upgrade. With the Windows 10 May 2019 Update, or version 1903, you have to go into Windows Update and choose to download and install it. That's why the number is still so low.
It will go up soon though. The only way that Microsoft will automatically install an update on your machine is if the one you're on is near its end of support. That includes Windows 10 version 1803, the version that the bulk of users are still on. Last week, Microsoft began the process for auto-updating people from 1803 to 1903.
The rollout is once again slow, on paper looking a lot like Windows 10 version 1809. The truth is, gone are the days of a new Windows 10 feature update being released and it immediately being installed on the majority of Windows 10 PCs. Microsoft is taking a more cautious approach these days.