Somebody who knows wine might have suspected it needed some air, but they wouldn't have known what the potential was at that point. There is a simple device called a vinturri that mixes the wine with air as you pour it into your glass. It seems gimmicky, but it really isn't. Its simpler than decanting and allows you to a/b without having to commit the whole wine. Some older wines can just fall apart quickly with oxygen, so its good to know beforehand.
Leaving a bottle open is slightly different than hyper-aerating (different rates of reaction produce subtly different results). But not radically so.