neowin[.]net/news/users-on-windows-10-version-1809-are-starting-to-be-moved-to-1909
Windows 10 version updates are now optional *unless you're nearing EOL*. Windows 10 v. 1809 is a bit over a year old now, and since it's supported for only 18 months, it's close enough for Microsoft to start slowly rolling out auto updates.