I'm not sure where you heard this, but it's factually incorrect.
One of my professors from undergrad at U of C did a great deal of research into the origins of the Stampede and it's certainly based on the authentic traditions of the ranching industry in Alberta prior to the formation of the province.
Ranching initially came to this area via the United States, as travel was far easier from Montana than from the east before the advent of the CPR. As a result, the area was heavily influenced by the American west. For a period of time, Calgary was a rough town full of brothels and gambling houses patronized by ranchers and cowboys from the surrounding area. The first mayor of our fine city is sitting on the right in this photo:
The ranching age had largely passed with farming taking its place by the time of the first Stampede in 1912, but the event was intended as a celebration of the roots of southern Alberta. If you'd like to learn more, you should read
Max Foran's book on the subject. It's a great read if you are interested in the history of this area.
Sorry for the tangent, but it bothers me when people misrepresent the Stampede as a made up event that's not rooted in the heritage of the city.