There have been lots of people asking "What is Android One? Why is the software on Android One phones different from different brands?". Good question. And unfortunately I don't have an answer, although I found this explanation on Engagdget: https://www.engadget.com/2018/09/03/android-one-faq-2018/
. I don't know if it is correct, but it seems like there is no fixed spec for Android One.
However, I think there should be. Google publish their compatibility definition documents (CDDs) for every new version of Android https://source.android.com/compatibility/overview
. These documents specify what a phone must, should and may be able to do (or not do) in order to be compatible with each version of Android. I found these when I was looking for information about Android compatibility with OMTP headsets (these were the type of headsets which came with Nokia phones before they changed to Windows Phone). The Android spec says that "If device implementations have a 4 conductor 3.5mm audio jack, they... Are STRONGLY RECOMMENDED to support audio plugs with the OMTP pin-out order." (this is for Android 9; earlier versions said "SHOULD"). But, AFAICT, my Nokia 8 does not
Now, I know that the 8 is not technically Android One, but it is supposed to be "pure", so it would be reasonable to expect that the 8 would support OMTP headsets, because it is recommended by Google in the spec for Android.
I don't know how to raise this point with Google, but I know I can raise it here - I think it's reasonable for us to expect that Nokia phones meet all Google's recommendations for Android phones, especially since they're running Android One.