The mechanism is redevelopment potential, not the rezoning notice itself. A lot that can now support a legal secondary suite or additional units is worth more to a buyer planning to add income, and an appraiser will factor that potential into the land component of a valuation even before anything is built.
There is a downside version too. A rezoning that increases nearby density can also change traffic, parking pressure and streetscape in ways some buyers discount, so the net effect on a specific property depends on exactly what changed and where the lot sits relative to it. Rezoning also feeds the tax side, since residential property in Saskatchewan is taxed on 80 percent of its assessed value, and the City of Saskatoon reassesses on its own cycle rather than the day the bylaw changes.
None of this shows up in an automated estimate, which values the house as it stands today and has no way to read a zoning bylaw amendment. Get your hand-reviewed valuation from Joel Dyck.