Very clearly looks like double yellow (Atari2600's footage/photo with sun reflecting) or faded white (Derek Kessler's recent photo), if you lack any previous knowledge. Even knowing what to look for, it is difficult to pick out the dashed lines in the video when looking through the forward camera. To be fair, I don't know if the NN's process the images in HDR or not, although the FSD chip does do tone mapping of the HDR images before they're passed to the NN I don't know if this means they're only getting a tone mapped SDR image or some kind of color / brightness corrected HDR image - so the NN may or may not be working with more than we see through the dashcam footage.
Even then, seeing some white dashed lines mixed in means nothing, since they're right on top of the reflective strips and when the light is reflecting off them they drown out the visible dashed lines to at least the point of confusion, if not loss. Keep in mind many places may have solid lines painted over dashed lines, so when the two are mixed, it is safer to assume a solid is intended. If dashed was intended, the solid should be removed. Derek's photo a human can probably make the jump to this being a single dashed line and not double white, but even then, if you weren't paying attention, you might be fooled momentarily.
Clearly in the repeater cams the dashes are only visible as the sunlight is not reflecting off them in the same way, but for the purposes of determining whether the lane is blocked off by solid lines, only the forward looking cameras are consulted (as unless you're driving in reverse, whether the lines behind you are dashed or solid is pretty irrelevant).
Perhaps some day it will use the rear facing cameras to determine that it must be reading the forward cameras wrong, but that requires a significant jump in logic and you must also be concerned about what if it was wrong, but then becomes right, but you're still treating it as wrong? You might attempt an illegal/dangerous maneuver in the time it takes to pass the point where you began crossing the lane boundary before the future markings become past markings that you can double check with the rear facing cameras.
It is unreasonable to expect perfection in this situation as most of the humans (well, I'm assuming) on who have commented they also see primarily a double line. Sure, it's annoying to get stuck in a lane and have the car fight you to change to the other lane, but as far as "failures" go it's a pretty human one.