The notion that the greenbelt is not restricting detached home development sounds like theory from someone with a job tile that contains "City Planning".  Most residents of the GTA don't travel to the "city" any longer and want housing choices increasingly unavailable.  The answer is not "middle-housing"  assuming Canadians need their housing options managed by planners.   The market has  role to play as much or more than "planners".   With detached home prices skyrocketing (high demand) and detached home construction modest (low supply),  planners have got it wrong so far.   Maybe they should get out of the city more often?