"concertinas are both unisonic and bisonic, the most common sytems are english anglo german and duet,"
?? And you read my post but for some reason thought I wouldn't know that?
The point of the sentence you quoted is that concertina is not defined primarily by the placement or type of reeds.
The OP is not concerned with type of reeds/ reed layout, but rather the available pitches on bisonoric models.
But it sounds like you've been hanging around the people who - let's face it, are a wee bit snobby - and so they insert this talking point about the "special concertina reeds in their individual chambers" to show off their knowledge of what is "proper." Yes, that *is* a feature that gives certain concertinas their unique timbre...a timbre that some prefer... but its a bizarre thing to jump in and emphasize when the talk is of the mechanics of playing the bisonoric instrument. Please tell the best woods that your Anglo-playing friends say are the best to make them out of, too. Because that's so much more important than what low notes I can get on the lower row of the the 30 key instrument.