It's quite possible that my relatives, even though they are zealous defenders of unschooling, have misunderstood this point somewhat, or have otherwise decided to revise Holt's original message for whatever reason. Unfortunately, a lot of ideas tend to take on a life of their own once they begin to spread, and the original inventor of the idea has little control over it; they may end up getting credit for ideas they never espoused, for better or for worse. I apologize if I've mischaracterized unschooling. Everything I know about it is based on what I've learned from my relatives.
To them, it's not quite about being inattentive to your children; quite the opposite. It's about giving them whatever they want. It would not be hyperbole to say that, in their view, a parent should serve the child much like a valet. So it's not that they ignore their children, it's just that they have infinite trust in their children to decide for themselves what is best. So, if they don't want to go to the doctor to get a shot, they don't have to. If they want to eat candy for supper instead of a nutritious meal, candy is what they'll eat. If they want to play instead of do chores, then they will play. They are never asked to do something that they don't want to do, because a parent is not allowed to impose their will upon the child. As such, the parents often run themselves ragged trying to keep up with their child's demands, and the children end up very spoiled and totally unprepared for adulthood.
From what you've described of John Holt's writings, it sounds like he and I would agree on a lot of things. I definitely believe in listening to your child's cues. I also believe in manipulating the situation so as to foster an interest. I'm not sure if he would agree with that or not. I call it a 'manipulation' because it's indirect: instead of directly insisting and pushing my child to read, I try to indirectly entice her into taking the initiative by showing that reading can be fun and rewarding.
In any case, I wouldn't put it past my relatives to misconstrue the true foundations of the unschooling movement, which is why I am always careful to add that I might not be understanding it correctly.