Just a quick comment on Jon Spangler's observations...
The longer "effective" top tube lengths on most Mixte bikes seems to be ideally suited to (and likely were intended for) flat Porteur-style handlebars and a more upright riding position. My own P18-c (which was specified with drop bars) forces an extremely long reach for the measured seat tube height of the bike.
I think the addition of drop bars fitted onto later models, was a concession for Ladies wanting to have a more "sporty" looking bike... perhaps this was mostly a marketing decision.
BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA