The rumor is that the Duo has been hardware-final since 2018. They were waiting for Windows 10X to be ready, but eventually decided to just launch it with Android instead of attempting to make a phone version of Windows 10X.
That explanation makes sense, if it's been in work for so long it's probably difficult internally to get the resources to bring it into line with current expectations.
Unfortunately v1 will probably bomb in its current state and we won't see the proper potential of the device.
Source: https://www.windowscentral.com/surface-duo-spring-summer-ear...