That's a good rundown you found, Robin. Thanks.
At the risk of saying something that was obvious to others all along: it seems that one upshot of this is Google will have location extensions running by default for all businesses with linked/shared accounts. Rather than having to go into the Extensions tab and enable location extensions if you want them to run.
That would be consistent with Google's recent rollout of dynamic sitelinks.
Google seems extension-happy, and wants you to use them even if you don't know what they are or that they're running on your ads. (Not that that's entirely bad; they are effective.)