Well, that's close. Actually the bypass ratio is defined as the mass flow rate (i.e. kg/sec) through the fan nozzle divided by the mass flow rate through the core nozzle. Since the two are different temperatures and velocities, the thrust ratio is somewhat different. (For a typical high-bypass fan engine, the fan nozzle accounts for 75-80% of total thrust)
So my questions remains. If this fan that is in effect nothing more than a shrouded propeller (fixed pitch, at that), providing about 80% of the thrust and regularly manages to get these aircraft to cruise at almost sonic speeds - then why aren't all aircraft designed with this ingenious high speed device?
I suspect it's very simple - the sheer excess in horsepower is providing these numbers. The abandoned propfan experiments showed that it did not suffer in speed compared to the shrouded fan, so it's certainly not the case that a prop can't be just as fast or effective.
I have a sneaking suspicion that if you designed an aircraft with exactly the same amount of horsepower powering either a shrouded fanjet, or an unshrouded fan/prop, they would probably be exactly as fast and fly as high.