That agreement requirement exists because the family home is protected. Under The Homesteads Act, 1989, one spouse cannot list or sell a homestead property without the other's consent, regardless of whose name is on title, which is exactly why the price has to be a joint decision rather than one partner's call.
In practice, most couples instruct a REALTOR® to run a market evaluation, then negotiate from there with their own lawyers involved, since a number both sides can defend tends to hold up better than one side's opinion. A hand-reviewed valuation is useful here precisely because it is independent of either spouse's interest in the outcome.
If the split of proceeds is contested separately from the price, that is decided under The Family Property Act and does not have to hold up listing the home. Get your hand-reviewed valuation from Joel Dyck.