I'm not familiar with the battery, but most batteries with vent tube fittings are Valve Regulated Lead Acid (VRLA), also called Sealed Lead Acid (SLA) and Absorbed Glass Mat (AGM) or gel-cell. None of those vent in normal use; if they are seriously overcharged the pressure valve lets go, it releases hydrogen and SO2, and dies very soon after that. That means if all goes well it makes no difference at all. If it goes badly the vent will contain corrosive gas that will attack cloth, paper, and many synthetics. The hydrogen is not a big issue in the absence of obvious ignition sources - it escapes quickly.

Yeah, the car makers like to add parts they don't need, especially vent tubes to run explosive hydrogen gas outside the vehicle. But a new battery without a vent and pop it in place. Then make sure no one ever smoke in or near your car. Avoid sparks, heat, etc.

Oh, and always wear a fire resistant suit.

It's not important at all, the car manufacturers just put it there to annoy you and cost you more money. Think about it, why would you want to vent a battery? Sounds ridiculous, right?

good luck

Garth- rock on