A deeper bed should allow more plants in the same square footage. They would compete for root space since there’s less volume.

So maybe they could only support 2 plants vs 4 type of thing.

One trick I’ve seen is to use some cloth bags on top of the dirt, gives more height and the roots will grow through the bottom into the bed.

Is it closed or open bottom? If you're just using it as a raised bed (open bottom) on top of usable soil it's fine. If it's closed, you'll want to stack a few open ones to give some more depth or you'll have short plants with not a whole lot of fruit.