As noted in the HN thread, the Ferrari was disabled due to an anti-theft device and couldn't be unlocked remotely due to connectivity. Lack of connectivity is not responsible for the car being disabled; an attempted "theft" (from the device's perspective) was, and a stuck car is exactly what the owner asked for.

Even if there have been a few historical software bugs that caused some Nests to change temperature, it did not "become completely unresponsive in the middle of winter". Worst case is you walk up to the device and turn the temperature back up. Also, there's nothing in that bug report that suggests it has anything to do with internet connectivity.

A quick google search shows plenty of people getting locked in non-internet-connected cars.

The modern world is complex. Even before I replaced my thermostat with a Nest, my furnace was already way more fragile than my fireplace.