That was true at the start, but not anymore. I take Route 6 every day which is one of the busiest non-transitway routes in Ottawa traveling up Bank Street in the old core (used to be the 1, but got renumbered). It's now almost exclusively double-deckers. They do have a longer dwell time, but that became moot because the route was so crowded that the logjam of people trying to maneouver around each other to get to the door made for long dwell times anyway. They've become so pervasive now (every new bus for the past several years is a DD) that the bus rider culture has adapted. E.g. people know to go downstairs one or two stops ahead.
There are a lot of low clearance areas in Toronto though, so it would limit their usage but not prevent it. What about increasing the number of articulated buses? Toronto's fleet is fairly small still, and I'm not sure if it's still true but when they were reintroduced the TTC increased the time between buses on routes they were on because they were bigger. Seems to defeat the point of adding capacity.
All the rail options are a long way away so there must be something more immediate that can be done.
