Yessirree, I understand that.
I would have to conclude that, if it is believed given that the extrusion itself has not been altered by the manufacturer, if the ERD is significantly larger the resulting BSD would be also.
However, I guess that is,again, making a supposition that may not be accurate.
For example: if one DYAD had an ERD of 596mm, that is no guarantee that another one will as well..