is a tacano. I don't think anyone is diputing that the PC9 "type" was the original platform that Raytheon started with . Raytheon then created another "type" called the Texan. Its identifier is different, Tex. It isn't unusual for a highly modified aircraft to be assigned its own type ID by the IKO treaty once it has been so heavily modified. An MD80 isn't the same as a DC9. They look very different. The Tex and the PC9 look different as well. The aircraft that you have observed flying are no longer considered PC9's. And if you saw a PC9 and a Tex sitting side by side you would understand why.
As far as the Tacano being an original design, that does suprise me. How did you find that?