I don't think that essay supports what you said. (It's incredibly well written by the way, thanks for linking it.) Near the end it asks:
> If you build a larger web service by combining network services that call each other over HTTP, rather than libraries or snippets of code linked or pasted together, does “Corresponding Source” include the source for those other services? What if each service is containerized, encapsulated in its own operating system? Do those operating systems count as “System Libraries” or “generally available programs” shield the application code they run?
Note that the author is asking a question here. It's not entirely clear (AFAIK, IANAL, etc) what precisely constitutes "linking" when it comes to the (A)GPL.
A thought experiment. Evil Corp takes a GPL licensed program and modifies it to communicate via file descriptors instead of linking with it at compile time and directly calling its functions. They proceed to distribute a separate proprietary product that makes use of the GPL program for many of its core functions. They claim that this isn't a violation of the GPL because they haven't "linked" with any GPL'd code. This is clearly a violation of the spirit of the GPL, but is it a violation of the letter?