Yes, that’s it. A lot of AV systems are dependent on high resolution 3d maps of an area so they can precisely locate themselves in space. So they may perform relatively well in that defined space but would not be able to do so outside it.

Level 5 is functionally a human driver. You as a human could be driving off road, in an environment you’ve never been in before. Maybe it’s raining and muddy. Maybe there are unknown hazards within this novel geography, flooding, fallen trees, etc.

A Level 5 AV system would be able to perform equivalently to a human in those conditions. Again, it’s science fiction at this point, but essentially the end goes of vehicle automation is a system that can respond to novel and unpredictable circumstances in the same way a human driver would in that scenario. It’s really not defined much better than that end goal - because it’s not possible with current technology, it doesn’t correspond to a specific set of sensors or software system. It’s a performance-based, long-term goal.

This is why it’s so irresponsible for Tesla to continue to market their system as “Full self driving.” It is nowhere near as adaptable or capable as a human driver. They pretend or insinuate that they have a system equivalent to SAE Level 5 when the entire industry is a decade minimum away from such a system.