This isn't taking something apart and copying it, they just sourced a KTM motor, cheesy for a company that developed the Hinkley series of engines, well regarded for their durability and reliability.
The idea that Triumph copied a Kawasaki is a bit of a misnomer. At the time the Hinkley engineers tore down most of the large multis getting ideas from all of them, some of the team came over from the car industry and teardowns had more to do with getting ideas to make the new motor more compact then it was to get HP or develop a valve train. Triumph got some help from Lotus engineering and some well known english engine builders for that. Starting with the Hinkley motor Triumph was the first MC manufacturer to fully adopt a modular engine design, 2 castings provided the basis for all the 3cyl models and one casting for the twins, a concept that came over from the auto industry with some of their engineers, all of the big brands do it now.
The KAW 900GPZ is the model rumored to be used as a basis for the Hinkley design but to say they copied it is like saying the KZ900 is a copy of a Honda 750/4