No, the ventilation box really has nothing to do with it, except the quart jars fit nicely inside. With the gallon jar, I just use a good old deep super with no ventilation holes.
To prevent the syrup from molding, you can add a Tbs of cider vinegar, some HoneyBHealthy, or equivalent.
The inverted jar forms a vacuum and does not drip. You should not use plastic, because it expands and contracts with temperature fluctuations and does drip.