Part of disclaimer at irs.gov for their interactive assistant: "Answers do not constitute written advice in response to a specific written request of the taxpayer within the meaning of section 6404(f) of the Internal Revenue Code."
The article does a good job of explaining why the list is small - and in my opinion quite useful in that regard. Agree that it would be interesting to know what perceived costs/benefits of various options considered were. I suspect accidents of history, before the need for a list like this was recognized, play a large part.
Your statement about your sample code is incorrect - just confirmed it for myself (cpython 3.8.3 is what was handy). Just add those print statements to the example in the article (before/after labels make analysis easier) and also add a set of threads that just do 'x = 0'.
So, if I'm reading this right, Quad9 is just a recursive dns resolver here. Why are they being enjoined rather than whoever runs the authoritative server?