The intersection appears to be at the bottom of a hill, not the top, as I expected based on Tesla's account re: white truck vs white sky.
I'm no traffic accident reconstruction expert but it appears to me that the top of the truck would have been below the horizon. Indeed, the photo is taken looking east, the direction the Tesla was traveling in.
https://www.google.com/maps/@29.4119817,-82.5444142,3a,60y,1...
If you squint or zoom-in, the light square on the right hand side of the road is in fact a vending-machine-stocking truck parked at a gas station on the other side of the intersection where this all happened, serving as a useful feature-height comparison; the semi was probably a little larger than that but similarly its wheels were likely underneath the horizon provided by the hill of the road. You can therefore imagine that more than half of the trailer might have been under the horizon of the hill, including wheels etc. -- frustrating any sort of machine visual inspection, 'cause that's even difficult by human eyes.
This Google Map image is 440m away from the actual crash site, which at 74mph corresponds to about 13.3s of reaction time. (The extra time from going at 65mph would would have only been an extra 1.8s.) It was intentionally chosen to be like "here is where a driver travelling East would have had no idea that there was a semi beginning to turn, pulling out onto the road in front of him."
The other data point needed is "here is where an attentive driver would have had no excuse for not knowing there was a semi in front of him;" that's about here:
https://www.google.com/maps/@29.4115366,-82.5429196,3a,60y,1...
This is 360m away, giving at least 11s of advance notice to the oncoming driver. Even with 5s of reaction time before he slams on the brakes, that should have been plenty of time. Clearly the inattentive driver is therefore a huge problem here, and the driver was presumably inattentive because he had been goaded by the ease of the driving system.
It's much harder to tell whether the semi should have seen the Model S and yielded right of way with this setup; as mentioned at 440m or so the Tesla should have been likewise invisible to a truck-trailer, so that's presumably when he would have started turning; it's not clear to me whether he would have then seen the car before his truck-trailer entered the oncoming traffic and he would have had no better option than stepping on the gas.
But it does sound like the Tesla's road detection is based on a visual algorithm rather than something more obvious like radar, and certainly both when you are too far from this sort of truck it can be nondistinct (as the road curves too much for you to see its wheels) and if you get too close it probably also becomes nondistinct (the closer you get the larger it is in your digital field)...