Safe is like 'secure'. It's a relative concept, and the level of safety we are willing to accept from products is something that should be communally decided and required by law.
We shouldn't go off expecting that someone elses ideas of safety will jive 100% with our own, and then blame them when someone else buys a product and is injured.
Should Telsa drive-assist deactivate and slow the car after 10 seconds without touching the wheel? Probably, but I won't blame them for not doing so if there is no regulatory framework to help them make a decision. It's certainly not obvious that 10 seconds is the limit and not 11, or 15 or 2 seconds.