I don't believe any of the current AP features have any dependency on GPS. Why would they? The car reads speed limits off road signs, and Autosteer and TACC are entirely based on processing the data from onboard sensors.What I find quite strange though is - when my GPS antenna wire was broken (frustratingly days after delivery), understandably both nav systems (and any browser location based services) decided I was stationary wherever I drove. TechSupport at the time confirmed all other data came in as expected when driving (gyro, etc) and the SvC later reported the loose GPS connection from the logs showed at most 1 lock, so I never got a GPS fix hence me being stationary for anything relating to location awareness - all makes sense to me.
What I do not understand is why my AP(1) functioned absolutely fine during that time - and acted no different once the GPS issue was fixed either.
My understanding (from a reasonably reliable source) is that the built-in satnav system is Navigon, but that starting in (?) v6.2 Tesla switched out the Navigon routing module for their own. So the maps are still Navigon, the instructions are still Navigon, the audio announcement files are still Navigon, the diagrams of junctions are still Navigon, the offline address database is still Navigon; it's just the routing engine itself that they moved to use their own code.
I don't know how route via superchargers works. Does it need internet connectivity? Does it adapt dynamically (i.e. suggest a different set of stops) based on traffic, or once you're on a trip does it think only about the next leg? Personally this is something I'd calculate on a server farm somewhere and then pass a waypoint list back to the car to render and provide the details.
These are pretty much the only class of issue I notice. I can believe that sometimes the car's suggested route isn't optimal (and maybe google or waze would do better), but that's not that noticeable.The really absurd routes like the ones above are, I agree, likely to be gross errors in the traffic data - but I don't think they occur very often and I'm not sure they occur significantly more often than other navigation providers.