In practice, one of two paths happens. Both spouses agree on a single appraiser and split the cost, which is faster and removes the argument about whose number is real, or each retains their own and the lawyers negotiate between the two reports if they land far apart.
The Homesteads Act, 1989 sits over the whole process, since neither spouse can sell or refinance the family home without the other's written consent or a court order, so nothing moves until the value question is resolved.
Starting from an accurate, documented number makes that negotiation faster on both sides. Get your hand-reviewed valuation from Joel Dyck.