Especially if it makes, "saves your engine" type claims(that's nonsense but an easy hook for sales). I also wonder if it would impeed what the vent is designed to do, expel air as quickly as a fuel nozzle pours gallons into your tank expelling a large volume of air.

My vent is just barely up to that task and can "burp" back, not a pleasant experience if you're over the filler blasting fuel into the tank.