The expectation is that FSD should not do stupid things that a normal alert human driver would not do like

1. drive straight into a concrete barrier https://youtu.be/Tr-oF7J0cBw?t=13

2. drive straight under a tractor trailer https://www.youtube.com/watch?v=9BgV-YnHZeE

In this instance

3. Come to a complete halt in a tunnel with busy high speed traffic for no apparent reason.

And the excuse that the driver should have been ready to take over within fractions of a second of the Tesla making a mistake while in FSD is absurd expectations on human reflexes and attention.