“Should have” is, at best, wishful thinking. In air filtration, a good rule of thumb is that, if an actual quantitative spec isn’t given, then the filter doesn’t filter. I’ve seen this with expensive commercial systems with stamped plans, I’ve seen it with very fancy European IAQ systems, and I’ve seen it with cars. Seriously, go look for a stated spec for a cabin air filter, which you generally won’t find, then drive on a freeway, bring a PM2.5 meter, and compare windows open to windows closed.