I've been reading this book (and enjoying it immensely), but it doesn't say anything about Junction workers being downtown office workers. It's true that the basic premise of the book suggests this is the case for many early Toronto suburbs which were later swallowed up by Toronto, but Solomon specifically cites the Junction as one of the exceptions, as an "industrial suburb."

On Page 19, he says "Suburban residents weren't all commuters, however. In the industrial suburbs, which sprang up partly to accommodate industries that were abandoning small towns, workers would live and work in close proximity, to save commuting time and the cost of public transit. A study of the Heintzman piano factory in the industrial suburb of West Toronto Junction (better known today as "The Junction") found that almost all its workers in the late 1880s could easily walk to work."

On page 76 he also refers to the South Junction Triangle as a "working-class [suburb], bult around factories located outside cities to serve city markets."

I don't think there's any doubt that over time, the Junction has indeed been more of a place where people commute downtown, but the basis of the Junction was as a self-contained village/town/city.