I know perfect is not qualitative. I've heard of perfect 5ths (you augment or diminish these don't you?) vs major or minor 3rds. What I've never heard of is a 'perfect' musical combination as including 3 notes. Unfortunately the OED did not quote what the chord being referred to was. Care to speculate on what 3 notes would have been referred to?

I would suggest that the real problem is some theorists insisting on a weird precision in language where is does not exist. For example in 1870 George Grove called a chord, "the simultaneous occurrence of several musical sounds, producing harmony, such as the 'common chord,' the chord of the sixth, of the dominant, ... etc., etc." That's it, 5 lines. Even by 1954 The lead sentence of 7 lines was pretty much the same, "the simultaneous occurrence of several musical notes, producing concordant or dissonant harmony." But it adds: "Certain of the more frequently employed chords have names of their own such as the triad or 'common chord'" and so forth. Emphasis mine. Doesn't say it can't be a chord just because theorists haven't named it.

Shall we argue about what several is? If you're referring to an indeterminate number of say 2-5 things for example what do you call it? I call it several. That's why a term like that exists. It makes no sense to tell Lucius that when he's holding these strings down it's a chord, but when it's those strings it's just playing the guitar. It would appear however that the new edition had to say be explicit about 2 because so many people need that precision.