Some tapers start right at the ferrule.
Some tapers go about 6"-8" at tip diameter before starting to widen.
Some tapers go about 12"-14" at nearly tip diameter before starting to widen.
Some tapers have a long radius between the straight part and the conical part.
Some tapers have a rather shorter radius between ...
Some tapers use a parabola instead of a radius ...
And many owners would need a dial caliper to see what taper is on the shaft they prefer.
So, in a technical sense, you are correct that the taper ALWAYS starts at the ferrule.
But in another sense, you don't/can/t feel the taper in your bridge until you are 8"-12" back from the ferule (European Pro taper)