I think it is just fine that we publish stuff using the different stores whatever.
But I can agree that the plugins/support for interface promising a lot but doesn´t really meet what you expect.
Yes you can export your work for later publish for mobile use. And yes it exists a facebook plugin and googleplay plugin. But no these plugins do not work for mobile use, they are only developed for web publish, they do not work for native android. And also no, they cannot be used for more functionality other than log in/log out. since they pretty much lack all other functionalities.
Both FB and googleplay has well docuemntet api docs, and I for myself has modified your FB plugin to be able to post achievements. But it is quite sad that I had to do that imo
just my five cents..