While it sounds like your question is rhetorical (Hey you guys are wrong), I will go into the technical side and practical side of what I am saying, and what it means exactly in longevity properties. It is a unique finish, after all. Water proof means if you insert something into water forever, no water vapor will pass through. Arrow Wood Finish will not subject to that, yet it is oil-based AND forms a unique structure that is not water proof, which for forever use and greatest versatility is a good thing. That's what I think.
Water vapor will pass through it which is a good thing when you have water vapor pressure difference: Taking the stock outdoors where it is comfy warm to a temperature of Freezing for instance. For a solid and brittle waterproof surface, like urethane it cracks the urethane and now the wood is unprotected where microscopic fracturing took place. Tung Oil also presents a problem in where the wood humidity level is different than the exterior humidity level, causing a pressure difference as well.
An extreme example is Arrow Wod Finish has been used to seal, protect and finish Green fresh cut wood, and it stays flexible as the wood shrinks and allows the water vapor to slowly pass through it as it slowly dries and the wood itself doesn't rot or split.
In other words the finish structure is gently porous to water vapor, but extremely water resistant. You can't leave the wood in a puddle forever without ruining the wood.
Conversely, over a 30 year time span, it holds up to normal use far better than waterproof, because it is a living finish keeping the wood "alive" and "content". - From a lasting point of view.
It is itself a unique physical structure that combines oil, filler, sealer, into a homogenous non-yellowing living-flexible finish that is extremely water resistant, doesn't create "white" marks when touched, but not too water proof.
It has a following amongst some gunsmiths because it does alot of things simultaneously fast. It has never made a print catalog, but exclusively demonstrated at various gunshows around the US for all of its existence. It also can work as a spectacular non-drying agent in place of the urethanes to keep guitar and violin wood sounding deep and rich and non-"tinny". At least that is the theory based on how flexible, water resistant, and long lasting it is. As a hybrid, it sets up so the finish doesn't need to be rejuvenated once a month or once a year forever, either, like oil finishes before the modern non-heirloom era. If finishes were put on to be passed down through the ages, you would be more concerned with all the properties, not only if you can leave it in under water forever. You don't store heirlooms under water. However you don't want the Finish cracking and the heirloom, cracking, or drying out over time. So water proof is how you define it.
Because it contains unique bonding properties, the less you use of it, the better it works - especially when you are going for the most brilliant Weatherby-style shine. The difference is without regard to the shine, the surface will feel smooth to the hands AND dull, or smooth to the hands AND whatever shine you select.
It is imperitive to follow the directions as to how little of it to use when, give proper setup time, etc.
You can flame me if you want, that doesn't make me a liar, and while it is only my word, my word has been upheld by a number of others across threads and sections, already here with reference to Moly-Fusion - also rather unique in properties, but for metal, not wood. It is unique, even if not the product everyone is talking about here.