Those prefixes aren’t material prefixes, those are quality prefixes. When you have a really ■■■■■■ Vladof, for example, it’ll be a “Rusty Sniper” or whatever.
For one, the chart has two different sets of info on it, it’s just wrong. Not all materials have prefixes anyways, at least as far as I know. Tediore, S&S, Jakobs, they don’t have them.
You probably never have seen an Obsolete Maliwan cause they’re all elemental, I assume the elemental prefix will always overwrite the low quality prefix.