That makes sense - for brevity I only shared the averages, but he also presented the data with the worst 7 bags thrown out so they must have know there was an issue with those seven.  
With the worst seven thrown out, the gas loss was 8.7% and the spoilage loss was 2.7% for a total of 11.4% loss.  I'd also expect bags to generally be better than bunkers for gas and spoilage loss (but not for spillage loss).