wish it were open source too edit:should have looked into it a bit more

Something I don’t see specified in that article is that the 66 million is for the number of Harmony OS 6 devices (the latest version) according to this Chinese article https://post.m.smzdm.com/p/a95dl2r0/

There are many more Harmony OS devices, but actually, that article says that most of them are still based on Android and only a part of the total Harmony OS smartphones run Harmony OS Next.

From the article:

@DoumiaoNotes analysis points out that among China’s approximately 800 million smartphones, about 150 million are active HarmonyOS devices, corresponding to a 19% market share; however, pure HarmonyOS only accounts for a quarter to a third of these, approximately 40-50 million devices.

user upgrade willingness is constrained by the completeness of application coverage. @HuaweiAndHarmonyOSNotes reminds users that while national-level applications such as WeChat and Alipay have completed deep adaptation, enterprise internal software or less common tools may not yet have a native HarmonyOS version. Users are advised to check whether their daily essential apps have the “native HarmonyOS” label before upgrading.

Also this English article says again that the 66million is for Harmony OS 6
https://www.huaweicentral.com/harmonyos-6-reached-66-million-devices/