It's pretty much how open source works everywhere - you have to convince the maintainer to adopt your code. If they don't, you've got the options of either being sad or forking it and trying to get people to use your subjectively better version.
In the case of AMP the only source that works with google is the official one. As soon as you fork it's not "AMP" compatible anymore.
You see the other half of AMP is completely proprietary and runs on Google's servers. It doesn't matter that you can edit AMP because the server (Google's end) will refuse to run your edited version.
Yes, which is what I implied: open source software is fine and good if it's used in a decentralized fashion.
But if it's just a provider open sourcing the implementation of their communication protocol/operating system running on their devices, it's good for the community that they can look into it and learn; but just as well, it doesn't imply that any of the changes you're able to make actually do anything.
But have anyone been able to convince the Android team of anything?
They are not even listening to the Linux team with their thousands of highly qualified developers and are essentially running their own fork of the kernel where everything has to be done The Google Way (TM).
It's open source, not anarchist source.