What the City of Saskatoon actually tracks is whether that below-grade space is developed and, separately, whether it is a permitted secondary suite. Neither classification depends on what you call the room, only on its condition and its permit status.
Below-grade area is still counted separately from above-grade area in a valuation, which is the real distinction people are usually reaching for when they ask about cellars versus basements. A 1,000 square foot bungalow with a fully developed basement is not treated as a 2,000 square foot house.
If a listing or an out-of-market source uses the word cellar, treat it as describing the same below-grade space Saskatoon simply calls a basement. Get your hand-reviewed valuation from Joel Dyck.