Sorry, you are WRONG!
If an Encore frame is purchased as a long gun it CANNOT legally be turned into a pistol. If an Encore frame is first assembled as a long gun it CANNOT legally be turned into a pistol. The exception would be unless one changed its designation through the BATFE which would involve a fee, paperwork and waiting; that route would not be worth it.
An Encore frame purchased/assembled as a pistol can then legally be changed into a muzzle loader, a shotgun or a rifle and then back again to a pistol legally.
This issue with the BATFE was settled over TWENTY YEARS ago.
You cannot legally assemble a rifle with a barrel less than 16 inches in length.