At the risk of becoming somewhat conspiracy-theorist-like, a possible benefit might be this: (from the ampproject.org FAQ)

How will advertising work on Accelerated Mobile Pages? (...) As part of that, those involved with the project are also engaged in crafting Sustainable Ad Practices to insure that ads in AMP files are fast, safe, compelling and effective for users.

If Google should at one point choose to block all non-AMP-compliant ads in Chrome, it might be a good idea to get into the boat early when "AMP-compliant" is still in the process of being defined.

It's even better idea to boycott it. Embrace-extend-extinguish may work for a big player but it will harm everyone else. We've been there before.

Pretty much everyone will want to be in the set of results that come up first when you search for something, and the cost of making something with AMP is really, really low. People could knock up a quick prototype very early on.

I expect that they've worked with people to figure out what makes the most sense to actually build and so the BBC and Buzzfeed would have had a bit of time before the announcement to start making the pages.