That makes sense to me. Glass being preferable since it is not permeable. I guess the key is knowing what constitutes short term and long term. In the case of the OP, 8 would be long term.
I read the same blanket rationale in relation to the fast fermenter. #1, it's an 8 gallon container, which...
http://beersmith.com/blog/2015/06/18/why-oxygen-is-bad-in-your-home-brewed-beer/
"Once fermentation is complete, a layer of carbon dioxide, which is heavier than air, sits above the beer and provides a protective layer in your fermenter. If you dont disturb the beer, that layer does a good job...