Sure, but it still requires the same kind of prescored lid; even with a key, I don't think that general design approach scales up very far while still not being too much of a hassle for consumers to bother with if there are competing products that are more convenient to open.
I agree, but if cuboids were the norm, I'm sure we'd come up with a better tool for them.
Expense may very well be a factor, but if that's the case, I'd expect an article like this to mention it.