Correct. The point of initial introduction, or at least where they were first found in the Columbia watershed, was in Canadian waters.
The reason I pointed to Boundary Dam is that they are in that river, the Pend Oreille and there are no fish passages in that dam. It is also right at the Canadian border as the river flows north into Canada as part of the Upper Columbia drainage. They could have been introduced anywhere up stream in the Pend Oreille river drainage. Haven’t been up there in decades but even back then there was an active program to eliminate them or reduce their number, even by netting them in the Pend Oreille.. Iike the Lake Trout in Yellowstone Lake, they destroy the native fish cuttroat populations, bass and trout in this case.