I'm gonna say he did not mulch first. I know the Walker is good at vacuuming but I have found that my Toro 62 with atomic blades are better at mulching. Then I take the Walker and pick up. I found a reduction of at least 10:1 if not greater depending on leaf moisture. That 63 hoppers would be 6 or 7 after a good shredding. I found it takes less work doing that and its easier on my old Walker which is still up to the task but I like preserving it.