Outdoor Gear Lab Editor's Choice: REI Co-op Traverse 35 backpack. Confirmation of volume capacity?

I noticed recently that Outdoor Gear Lab had rated the REI Traverse 35 an Editor's Choice as the best day pack for heavy loads. This pleased me greatly because I picked one up about a year ago, planning to use it for lots of trips, but particularly for paleontological field trips, when hopefully you come back with a heavier pack that you started with, bulging with paleo goodies.

But I was surprised to note that they gave the T 35 a capacity of 48 liters, while you rate the T 35 as, at the most, 37 liter for the large size...What gives?  Is the difference the open stash pocket, a typo, or what?

I am very happy with the pack, which I purchased on sale for half price and it has served well, although I can't use it to backpack the largest specimens.  The stuff we collect ranges from trivial (stuff it in your shirt pocket) to much bigger.  The largest weighed a little over 800 pounds and I alertly decided against putting it in my wonderful Traverse 35.