I don't have an Aeronaut of either size, but I ordered one LSS in each size to see for myself, as the video is tantalizing but doesn't show the interior. Indeed as many of you speculated, there is a bucket-like layer of dyneema material (kind of like the base of the travel tray) that stays sewn to the equator of the bag. You can push clothes in from either side. It didn't strike me till now, but these could be used simply as larger single-receptacle travel stuff sacks as they are quite long. The inner labels read 5 and 6 - does that indicate these are larger? The largest stuff sack I have otherwise is labelled with a 4.
I think the key decision is whether you want the contents of your stuff sacks to abut each other. I could also see these being useful as shoe bags. I haven't yet put shoes in my TB bags without covering them, with the exception of pool shoes in a Nordic shop bag (get it, blue for the water?).