In regard to disability, I think there is sometimes some confusion. “Single exit” refers specifically to what's known in building codes as “the exit”, which is the stairway. It doesn't speak to how many elevators or whether or not there should be an elevator. My understanding is that building codes in Canada, at least for what are called part 3 buildings—that is, larger buildings—generally require elevators, and those would remain required.
A general fact about housing is that newer housing is always more accessible and generally safer in every way than older housing. The details of how you regulate newer housing are not quite as important as new versus old. To take a concrete example, older housing in British Columbia, including Vancouver, is much less likely to have an elevator. It's much less likely to have step-free thresholds for getting in and out of units. The actual standards are much lower. The electrical standards and clearances for turning wheelchairs or whatever in kitchens or bathrooms were much lower back then.
You have to weigh the smaller details of new construction against all of the improvements you get in a new building to begin with, so—