That ended its life in 10.12.6 as version 0.3, or, expressed in subsequent numbering, 249.7.6. MacOS Sierra already had a pre-release version for those who wanted to preview it. Had a significant percentage of conversions gone wrong, Apple would have had a disaster on its hands, particularly as it didn’t admit to doing this until WWDC just over two months later, when it announced that APFS was coming to macOS 10.13 High Sierra that September.
When it rolled out iOS 10.3 that day, the installer silently converted the storage in each iPhone and iPad to the first release of Apple’s new file system, APFS. On 27 March 2017, Apple made one of its biggest corporate gambles.
