The more you "disconnect" as a driver, the less likely you are to take over in a split second and this has been proven again and again with humans. A system that works 90% of the time is probably the worst because it's good enough to give you confidence but bad enough that it's a false one. The driver is in the position to buy the advertised "you can disconnect" feature but then only be able to use it under explicit risk of harm to themselves and others. It actually increases the mental load as drivers will try to both "disconnect" (type on the phone, watch a movie) while also "paying attention to the road". Of course both can't be reasonably done at the same time so both experiences are sacrificed.
It's like encouraging people to take a taxi after drinking but then expecting them to take over whenever the driver makes a mistake and holding them responsible and accountable for the outcome. You won't enjoy the drink, or the drive.
These half-way solutions are great for marketing and for people who are all about the hype. But not only are they the bad compromises, they're also fueled by bad and incomplete data, and by marketing departments wanting to sell more. Almost no self driving outfit provides data on how many times did a human make the slightest correction while the self driving was enabled. Or out of all possible driving conditions, what percentage of them were covered by those self driving miles.
My personal philosophy is that cars are either self driving or they're not. Meaning they can either match an average human driver in all conditions they're expected to encounter over the lifetime, or they're just assisting the driver. If it's self driving except when it's not then it's just like a student driver. You wouldn't confuse them with being perfect drivers just because of their perfect safety record, given the supervisor corrects their every mistake.