Accelerated Mobile Pages: great for SEO, bad for control

John Gruber, back in October:
Can someone explain to me why a website would publish AMP versions of their articles? They do load fast, which is a terrific user experience, but as far as I can see, sites that publish AMP pages are effectively ceding control over their content to Google.
In theory, Accelerate Mobile Pages are just highly optimised versions of your pages, that perform very quickly on mobile, and which live on your sever. The problem is that in many cases Google is saving them to its own cache, and then presenting the cache URL to visitors:
One of the biggest disadvantages for publishers in using AMP â the accelerated mobile pages format â is that Google will not show a publisherâs actual URL when displaying AMP pages. Google says this is so AMP pages load quickly.
Traffic & Revenue: yours to keep
This doesnât lead to a net loss of traffic or ad revenue, as long as youâve set up your AMPs properly. Sullivan again:
If you have AMP pages properly configured with analytics, ads and other goodies you might want, the traffic remains essentially yours. The cached URL might be shown, but everything on the page remains in the publisherâs control and is served from the publisherâs own site. It is your page, except for the URL.
And, in many cases, acting on the cached URL will bring you back to the true one:
As for the URL, it will redirect to a publisherâs site if someone tries to go to it directly (though as a 302 âtemporaryâ redirect, rather than a 301 âpermanent,â which I feel would be better). AMP pages themselves also carry a form of source attribution in their canonical tags. Should someone share an article using options within the actual article, the publisherâs URL is used.
When Sullivan says âthis feels oddâ heâs essentially saying âwrongâ, but couching it more gently, as his readers like Google. However AMP is not popular with people who like to share links, because it all goes back to Google, not the publisher.
The AMP trade-off
Iâve had multiple reports from publishers â especially niche publishers â that implementing AMP has led to a very significant growth in traffic from search. I serve AMP pages here (hereâs this post as an AMP) â and when I remembered to add analytics to the AMP pages I was surprised how much traffic they were delivering. So, right now, youâre making a trade-off if you implement AMP â youâre giving up some control over your URLs in exchange for traffic.
For some publishers, thatâs not a good trade-off:
Today we removed AMP support from MacStories. Our site is already fast, but, more importantly, no one messes with my permalinks. Feels good.
â Federico Viticci (@viticci) December 12, 2016
And, quite frankly, I canât see a good reason why Google couldnât make this less difficult. Sullivanâs research suggests that Google caching the AMPs isnât helping land times significantly â who why is Google so focused on doing this?