Tech companies have to at some point say they don't want to lock their users in. Usually this comes toward the end of a cycle, when they've been building up lock-in because the users weren't thinking about it. Eventually users start wondering why when they post something to one service they can't also post it to another. Or why they have to use one vendor's lame version of something another vendor does much better. So they have a press conference where they bring up smaller competitors and get them to say everything is great, when the truth is that it isn't great at all.
That's how you get formats like AMP. Put LinkedIn, Pinterest, Google and Twitter in a room and start with this agenda: 1. Let's make a new open standard we all support. 2. But do it in a way so we don't undermine our individual lock-in. Obviously these are contradictory goals. If you look for the intersection between the two sets, it's very very small. But you try to make it look bigger with fancy language and lots of big names supporting it. And shrimp! Lots of shrimp, and cocktails.
Because they're scared of something.
In this case that something is Facebook.
Each of them has a product that's threatened by the huge size of Facebook and their new interest in news, and their recent track record of spinning off components of the core product, or acquiring companies that compete with them.
The big news orgs need to get their name out there so their board members, shareholders and employees don't get the idea that they're being confined to ever-smaller spaces by the tech giants (which they are regardless of how it looks).
It's caching. You can use their caching if you conform to certain rules. If you don't you can use your own caching. I can't imagine there's a lot of difference unless Google weighs search results based on whether you use their code. That's Google behaving an awful lot like Microsoft of the 90s. Ultimately that kind of trickery leads to new more free-wheeling options, as Google itself was to Microsoft in the following decades.
Round and round we go!