Slimmer cables on superchargers are Tesla being clever and pushing more amps over the cable than the cable is rated for, and monitors when the cable overheats. Everyone else seems to do it by the book and has cables thick enough for their max amperage.
BTW, CSS2 supports 3-phase AC charging, which is common in Europe, but not in the US. In this regard NACS would be a downgrade for Europeans.
Maybe, but over billions of charging hours I have not heard of any stories about chargers catching on fire yet. I have to assume that if one of them did catch on fire it would be all over the news, the media is starving for anti-EV stories.
Assuming it's true, then probably the sensors are fail-safe.
But I'm not totally convinced Tesla is going over the cable rating. A lot goes into the rating of a particular cable -- everything from conductor material and size to the insulation around the conductors, proximity of conductors, etc. Not to mention the liquid cooling. It's plausible that supercharger cables are rated for more than 600A.
BTW, CSS2 supports 3-phase AC charging, which is common in Europe, but not in the US. In this regard NACS would be a downgrade for Europeans.