Author here. Appreciate your perspective. I find large backlogs get stale quickly, and what was important three months ago is often not the case as context has changed. If I have a good ear to the ground I've discovered that there's usually something more valuable that can be delivered, and the way I've discovered is through talking to people.

Your point about "directly informed and refined by customer feedback" is well-taken, but in my experience a large backlog is rarely that, but more a dumping ground that seems daunting. Of course it depends on who is managing it and how, but more often than not I've seen PMs succumb to big backlogs rather than make it a well-vetted list maintained proactively like you have stated.