> at no point does it read my data
Tracking doesn't require reading any of your data. All that is necessary is to trigger some kind of signal back to Google's servers on whatever user behavior they are interested in tracking.
> or communicate with third parties
Third parties like Google? Which is kind of the point?
> [example source code]
Of course you can generate examples that are trivial to inspect. Real world problems are far harder to understand. Source is minified/uglified/obfuscated, and "bad" behaviors might intermingle with legitimate actions.
Instead of speculating, here is Google's JS for AMP pages:
https://cdn.ampproject.org/v0.js
How much tracking does that library implement? What data does it exfiltrate from the user's browser back to Google? It obviously communicates with Google's servers; can you characterize if these communications are "good" or "bad"?
Even if you spent the time and effort to manually answer these questions, the javascript might change at any time. Unless you're willing to stop using all AMP pages every time Google changes their JS and you perform another manual inspection, you are going to need some sort of automated process that can inspect and characterize unknown programs. Which is where you will run into the halting problem.