That's not at all true, as neither Spadina nor St. George are at heavily developed intersections. Nothing at Spadina is taller than three stories: it has commercial lowrises on the northeast corner, a park on the southeast corner, and lowrise apartment building on the northwest corner. The Jewish Community Centre is the only major building at that intersection, and even it is only three stories.
The St. George station area is a bit more developed, but the highest building there (the UofT residence) is a relatively recent addition. I don't know that the Bata Shoe Museum counts as a "highrise", and as far as I know the mansion on the northeast corner and the building on the northwest corner have both been there since before the station.
In other words, I don't think that interchanges necessarily mean heavy development, and Pape and Danforth currently has development density comparable to (if not greater than) that at Spadina Station.