There is certainly a maximum ODD for human drivers. It's all conditions where the road is navigable (ie not flooded or iced over) and visibility is good enough to see.
But L5 ODD already encompasses all driver manageable road conditions with no restrictions whatsoever. The only ODD that would be greater than L5 ODD would be one that involves non driver manageable conditions.
L5 ODD:
"“Unconditional/not ODD-specific” means that the ADS can operate the vehicle under all driver-manageable road conditions within its region of the world. This means, for example, that there are no design-based weather, time-of-day, or geographical restrictions on where and when the ADS can operate the vehicle. However, there may be conditions not manageable by a driver in which the ADS would also be unable to complete a given trip (e.g., white-out snow storm, flooded roads, glare ice, etc.) until or unless the adverse conditions clear. At the onset of such unmanageable conditions the ADS would perform the DDT fallback to achieve a minimal risk condition (e.g., by pulling over to the side of the road and waiting for the conditions to change)."
You seem to think that the ODD for humans is a binary thing, but that's not the case. There are a great many situations that impact whether one human continuous on with a journey compared to another.
Sometimes the people that get off the road have anxiety with whatever they're being faced with. Like the first time I drove my camper van I decided it was best to stop for the night when I saw a lighting storm ahead, and the wind was throwing me around. The road was navigable, and the conditions didn't dictate that I got off the road immediately. I chose to do so mostly because I felt like things were getting worse.
There have been plenty of other times where I drove in bad situations, but only because of more familiarity with the situation at hand.
Lots of times its not a binary case as usually when that happens the roads themselves get closed. But, it's simply a judgement call based on the information we have at the time. Sometimes its based on prior knowledge like if I know a bridge typically freezes over in such and such conditions. So I simply won't drive on the bridge in these conditions, and later on I'll read in the news that 40-50 cars had some pileup on that bridge due to it.
In the camper van case it's likely an L5 system would have continued on assessing the situation not based on what it thought human drivers would do, but based on a design element. Like if estimated cross wind speeds are greater than this then we shouldn't continue.
In the other cases I likely exceeded the ODD parameters that would be practical for an initial L5 car.
Short term my expectation from L5 (when they get released) is they'll have ODD limits that seem overly careful.
Long term my expectation from a L5 vehicle is that they'll exceed the ODD capabilities of even the best human drivers because they'll have better sensor equipment. Like instruments that can see through fog, and more connectively to what's happening with tires.