Scott, spooned the way I was always taught is how I described it. It is not a good thing, usually is narrow and unremarkable. Collies and borzoi often have the same issue and fanciers in those breeds refer to spoon jaw the way I did.
The example you posted as "spooned" I would hardly consider faulty, and the one you called square, I would called a bit shoveled.
But that is nit-picking.
Regardless, I think if you want to assign a nickname to the jaw in the first picture, do not use "spooned" I know if I was just told without seeing that the dog had a spooned jaw I would visuialize a completely different thing.