Level 2 sustains steering and speed but the human must monitor continuously. Level 3 performs the whole driving task but hands back to a human on request. Level 4 performs it including fallback, within a defined operational design domain. Level 5 does so anywhere.
The meaningful boundary is between 2 and 3, because that is where legal and practical responsibility transfers from human to system. Every consumer driver-assistance system on sale today is Level 2, whatever it is called.