I'm sure the other statement was made with the same confidence. Downloading doesn't have to be for listening today. In the future we may not have the same hearing limitations.
In short the overconfidence is a result of not imagining a future that's different than today.
Or, without needing a far flung sci-fi future, the concrete impact of frequencies under 50hz on frequencies above 50hz. Particularly as it applies to the resonance of a listening environment. Maybe you won’t notice in your headphones, but on a PA system in a physical space, e that indoor or outdoor, there’s a measurable and discernible change to the audible frequencies based on the existence or non existence of the inaudible ones. The same applies on the high end, but it’s less practical of an example, and I’m not sure half of people would care to listen long enough to notice.
In short the overconfidence is a result of not imagining a future that's different than today.