Edmonton recently outpaced Toronto in housing development on an absolute basis with much lower housing prices and less than 1/5th the population!
The same cannot be said of Toronto (or everywhere else in the nation that isn't the Prairies for similar reasons), for landed interests and the bureaucracy and corruption that comes with them are a lot more entrenched in that area.
Those are the two factors explaining the housing starts, not the ineffectual rent control that exists in Ontario.
Toronto has a cumbersome permitting process that runs from months to years, while Edmonton's process is mostly automated and grants permits within weeks.
Regardless, the other relevant factor here is the actual price of housing, which is substantially higher in Toronto... and yet Toronto struggles (by design) to build anything.