There's no such thing as "direction" when you're talking about sidewalks or PATH. I don't see any lane markings on the ground. Talking about taking advantage of "capacity in both directions" 100% disingenuous. If that is how the department of planning is thinking then god help us all. Their batting average is low as it is.
Clearly there was some confusion about what taking advantage of capacity in both directions meant. I will try to explain, although this may be difficult without a diagram (I am neither good at photoshop nor do I have time to draw one at the moment).
Of course there are not lanes on a sidewalk or in the PATH. However, there is a limited width, and therefore a limited number of people who can traverse in that space. Right now, assume all of them are coming north from Union (not accurate, as many are coming from King or St. Andrew, but a two-point analysis will demonstrate the excess capacity better). Some people coming North along Bay get off at the RBC Centre, some at First Canadian, some at Bay Adelaide. Assuming that PATH/sidewalk capacity is fully used at Union, and an equal number work at each of those three areas, but the sidewalk/PATH capacity is the same in each location, you have 2/3 empty capacity at Bay Adelaide. Bay Adelaide is close to Queen Street. If there were a subway alignment at Queen, many people would get off there and head south, using the empty capacity between Queen and Adelaide. If the subway were put to the south, then the already crowded areas would become more crowded or overcapacity, creating a choke-point that would render that commute less efficient.
In the evening, when people are going home, the excess capacity is opposite, (i.e., heading north to Queen) and would be used again with a Queen Street alignment.
I didn't take the time to explain this so clearly earlier, because to those of us actually working downtown every day, it is intuitive. At 8:30 in the morning, it is obvious that one would rather walk southbound on Bay Street from Queen to Adelaide, than northbound from King to Adelaide.