We've never used different APKs for different architectures for any of our games, but want to try and help. The Google Multiple APKs document states "Google Play then supplies each APK to the appropriate devices based on configuration support you've declared in the manifest file of each APK" so it looks like you need to have some differences in each App Manifest file between your different versions.
As for what those differences are, the best info we could find was how they work with Filters which are described here and in more detail here. Good luck and we hope you can get it to work.