The story he's talking about has happened on a few occasions, and Tesla learned from them.
In 7.1 the AEB (the emergency stop function) wouldn't activate if you already had your foot on the brake. In 8.0 the AEB changes that behavior to increase stopping power. So you can't accidentally override the AEB by hitting the brake. The throttle still overrides it.
In 7.1 the Autopilot radar did not see stopped objects. In 8.0 it has the ability to now see them, but it won't slam on the brakes for them. It might activate FCW, but I don't know if it does.
In a future version of 8.X Autopilot it will activate stopping for a stopped car. The AEB system will also activate for a stopped car. This activation hasn't been implemented yet because they have to do the whitelisting to make sure it doesn't falsely activate for road signs, etc. I believe the main purpose of 8.0 is to create the whitelist, and 8.1 will be the full implementation.