I hate to be sanctimonious at people online but this is how people get killed. Is it not illegal to do this where you live? In the UK you'd be half way to losing your license if you got caught touching a phone while driving (and lose it instantly if within the first 2 years of becoming a qualified driver).
You just said it yourself, you can't trust it, so don't play with your phone while driving, lane assist or not.
Lane assist has also led me to be much better about always signaling lane changes lest the steering try to fight me.
That's exactly what the tesla driver must have thought too. Right until the auto pilot steered directly into a barrier. Volvo S's system may be better, but any lapse in attention can lead to the type of crash we are discussing about.