Thank you so much for your comprehensive and well considered explanation!
I must admit that I had quite similar feelings that that object might be dysfunctional, composite, or a fake when I first saw the catalog offer and so I decided neither to view or purchase it; I not even asked for aditional images, which I usually do when I see something of deeper intrerest.
Like you, the dissimilarity between what usual period grape shots look like - just as you ascertained, they are usually heavily packed forming a firm and integral unit - and the appearance of this item, both outward and inward, struck me. For a span of time, I was uncertain whether to put it up for discussion or not.
Anyway, for more information on the usual types of grape shot, I would like to recommend referring to my thread