We poked around the Internet, thinking that surely someone else has wondered about this and found an answer. But no luck.
The closest we came is people wondering why cans of cranberry sauce are often upside down - another longstanding kitchen mystery! The conclusion there was because whole cranberries tend to settle on the bottom. By opening the bottom, you’re presented with the beautiful cranberries. (This doesn’t, however, explain cranberry jelly.)
We wonder if something similar might be true for tuna. Perhaps the fish becomes compacted during canning and then over time on your shelf, with the packing liquids rising to the top. By opening the bottom, you see the packed tuna instead of the cloudy packing liquid.
Is it all aesthetics, then? But why some cans and not others?
What do you think?
(Image: Emma Christensen)