The charts are not reporting what happened during the flash crash, they are for a separate, later event that they chose to see if the behavior was regular. It was, but not to the levels seen during the flash crash, as is to be expected from the cause.

This is not about a time when some technology broke under extreme load, this is about a broken system that persisted in that state for an extended period of time, and it was broken in a way that made it no longer compliant with the law.