However, it's also be demonstrated the the ducts can stretch and flex under pressure (as through medical procedures with balloons and stents). Up to 20 mm as I recall, medically documented. I believe the Liver Flush procedures can create that kind of pressure, and many people have reported large stones coming through.
Again what you can force and what will happen naturally are not the same thing. Are you aware of the fact that a strong electrical shock can cause the muscles to contract so hard that they can snap your bones? Does that mean you can snap your bones by simply flexing your muscles? Of course not!!! So to compare a forced dilation with a catheter to a natural dilation is simply ludicrous and shows clear desperation.
By the way, since the ducts can be forced open so wide with a catheter then how do you explain so many cases of much smaller stones actually getting lodged in the bile ducts? After all according to your hypotheses these smaller stones should have simply backed up pressure and the ducts would have dilated larger than the stone allowing it to pass. So according to your hypothesis we should have a hard to impossible time finding cases of lodged stones in the ducts. Yet they are easy to find since the ducts don't dilate that large naturally!