No, the myth, at least as it was told on SSP, was always due to the incorrect calculations provided on the Downtown Calgary wikipedia page. I have since recalculated and sourced my calculations and definitions correctly. However, that old incorrect information was online for over 10 years, so the perceptual damage is already done.
If you're correct about the extended downtown population being around 60 000, that would mean Calgary has a very large core population for a city our size. So that again is the reality of the situation further dispelling the myth. The fact that we have a downtown with 50 million square feet of office space is merely a testament to our boom/bust (with a greater edge to the boom) economic climate in which the city exists, and should have no bearing on the amount of population we have downtown. If anything, it may be a detriment to getting population downtown due to land values being way higher than they ought to be in a city our size.