This is the crux: "this move by Google is to ensure that device makers can’t simply bypass Google’s CTS and ship devices with the promise that users can simply

This is the crux: "this move by Google is to ensure that device makers can’t simply bypass Google’s CTS and ship devices with the promise that users can simply side-load Google Play apps and services. Doing so will now bring up these warnings which will shame device makers and force them to go through the proper certification channel."