If the house was the deceased's principal residence right up to death, the principal residence exemption can shelter the gain up to that date, though this is a decision usually made with an accountant since it interacts with any other properties the estate or beneficiaries hold, and getting it wrong, or filing late, can add CRA penalties of 5 percent of the balance owing plus 1 percent for each month it stays outstanding.
If it was not sheltered as a principal residence, for example a rental or a cottage, only 50 percent of the capital gain is taxable and added to the beneficiary's or estate's income for the year, taxed at their marginal rate rather than at a flat rate the way some other jurisdictions apply.
None of this changes what the house is actually worth today, which is a separate question from the tax calculation. Joel Dyck's hand-reviewed valuation gives the estate and its accountant a defensible number to work from, built on comparable sales rather than a rough guess.