He means that working from home implies quantity of work is less important than quality. Nobody knows how much time you put in, but yourself. One way or another, you will be judged on what you deliver, not how much time it took you.
Some managers (or even people hiring contractors) think they can get around this, but, ultimately, you can always do in 4h what they expect you to do in 8h and get paid for 8h. Not saying it's moral, but it is the reality. The conclusion is inescapable: working from home implies that the only important metric is the quality of your work (and the deadline), not how much time you spend on it. Because you can "simulate" one with the other.
Some people don't realize this, yet. Doesn't make it not true.
EDIT: PS: I'm talking about project where the "deadlines" are reasonably far apart and predictable. Say, no more than a few times a day. If your work includes being on-call and responding to incoming requests, that's a different story.