The Progenitor may be a one of a kind device that wasn't finished during the Time War. After the Time War, the trio of Daleks from "Victory of the Daleks" discovered the Progenitor and finished it off.
Also the Daleks said one survived so maybe there were many that were opened
The Daleks implied that several, possibly many, Progenitors had been hidden around the universe as a racial insurance policy but they clearly stated that "only one" survived.
It seems extremely likely that the Time Lords would have hunted down and destroyed every Progenitor they could, in an effort to prevent the Daleks replacing casualties. In the (lost) 1966 story "The Power of the Daleks", there was a production line churning out new Daleks at a considerable rate. One part of the line produced the casings; another produced the biological creatures, which were then placed in the casings. That production line was severely limited by a shortage of materials and power, so a Progenitor with plenty of both would presumably have an extremely high rate of production. The Time Lords would not have liked that one little bit.