Found a side camera video in a very similar situation from greentheonly. He got it from a salvage wreck so the video is from a crash caused by humans driving, to be clear nothing to do with autopilot. The oncoming car is clearly visible beyond 110m. Note this video has been compressed once by Tesla, once by Twitter, plus anything green did, so the original source video that the computer processes would be higher quality.
Watch the 5 second video here
https://twitter.com/greentheonly/status/1258599345731129346
At roughly 1 second the white car appears across the highway to the right of the side rail. Much easier to see in video
https://i.imgur.com/fOxZXkr.png
https://i.imgur.com/olIzkd5.png
Lines up with this intersection on Google Maps. Measured to 110m being very conservative.
https://i.imgur.com/K2ekZz3.png
https://i.imgur.com/2jmLtsB.png
edit:
You can also barely make out an oncoming car in the other direction from the left pillar footage
https://twitter.com/greentheonly/status/1258712314360070146
Using the same technique I guesstimate the dark oncoming car is visible around 190m based on using the upcoming intersection signs as landmarks and comparing to google street view.
After watching these videos I think far off oncoming vehicles are actually relatively easy to see and detect as long as you can look at the video and not still images. Stands out very clearly against the background and seems like something a technique focused on labelling moving objects would have little trouble with.