Level 5 isn't feasible as much for legal reasons as technical ones.
I don't think any company wants to sign off on the notion that their software will handle all classes of problem, even ones they have no data for at all.
> Level 5 isn't feasible as much for legal reasons as technical ones.
That point is taken into account under J3016_202104 § 8.8:
“There are technical and practical considerations that mitigate the literal meaning of the stipulation that a Level 5 ADS must
be capable of ‘operating the vehicle on-road anywhere that a typically skilled human driver can reasonably operate a
conventional vehicle,’ which might otherwise be impossible to achieve. For example, an ADS-equipped vehicle that is
capable of operating a vehicle on all roads throughout the US, but, for legal or business reasons, cannot operate the vehicle
across the borders in Canada or Mexico can still be considered Level 5, even if geo-fenced to operate only within the U.S.”.
I don't think any company wants to sign off on the notion that their software will handle all classes of problem, even ones they have no data for at all.