There's also the fact that the Android VM can't do certain things that Android phones and tablets can. As an example, files management in the Android VM is so bad that I lost access to standard access for months due to a bug...
Also, the Android environment is all the way back on version 11. If your theory is correct, that Google wants to move third-party developers to Android, then they're doing a terrible job of it. Android devs haven't and won't target all these outdated devices.
I believe Chromeos is becoming an enterprise/edu only platform. That would explain the (new) lack of interest in development and focus on security at the cost of all functionality. This is a new development and wasn't "always" the case as you claim, because many of these apis are as old as Chromeos itself (10-ish years).