A retirement income is the most predictable deposit stream there is. Social Security lands on a known Wednesday, the pension lands on the first, and neither one gets laid off. As raw material for the deposit side of this strategy, that beats a commissioned salesperson's income. So the answer isn't no. It depends on three things, and none of them is the deposit.
First, the surplus. Dynamic Banking runs on the gap between what comes in and what goes out, and it does nothing at all without one. A retiree with $4,200 coming in and $4,100 going out has a $100 surplus. A hundred dollars a month against a mortgage is a hundred dollars a month against a mortgage, whether it routes through a line of credit or not. Work out your real number using twelve months of statements from both accounts, the way find your real monthly surplus lays out. If it's thin, stop here. This doesn't create surplus. It routes the surplus you already have more efficiently.
Second, qualifying. Retirement income counts, and some lenders will gross up non-taxable Social Security, which means they treat it as a bigger number because you don't pay tax on it. That helps your ratios. Award letters and 1099-R forms stand in for pay stubs. What gets people declined is the debt-to-income calculation when a pension is modest. The fix is often an asset-based program, where the lender treats part of your retirement savings as if it were monthly income. Ask for that by name if the first answer is no. What lenders look at before they give you a line covers the rest of the file.
Third, and this is the one I'd think hardest about, the repayment period. A line of credit has a draw period, meaning the years you can borrow and pay interest only. When that ends, the repayment period starts and you have to pay the balance down on a schedule. Open one at 68 with a ten-year draw period and that switch happens at 78. The payment can double or triple, it lands on an income that isn't growing, and it lands at an age when refinancing out of it is harder. Find the draw period end date on your disclosure and work out what that payment looks like against your income in that year. The mechanics are in draw period vs. repayment period.
Rate risk lands differently in retirement too. When a variable rate moves two points against a working household, they can work a little more or spend a little less. Against a fixed income, spending less is the only lever there is. So the version I'd run at 70 is smaller and more careful than the version at 40. A line of credit sized to a balance you could clear out of savings if you had to, used for routing the surplus, with no large chunk left outstanding for years at a time.
There's also a change in the goal that's easy to miss. Before retirement, you're trying to shorten the payoff term. After retirement, you're usually trying to lower the monthly outflow, because outflow is what a fixed income has to cover. Those two goals point at different moves. Paying the mortgage off entirely removes a payment. Chunking a mortgage you'll still be carrying at 85 shortens a term you may never use. Decide which one you're actually buying before you open anything.
For a lot of retirees the answer is a line of credit that sits open and funded and mostly at zero, used for the roof and the medical bill and the year the market is down. It's a smaller ambition than the full strategy. At the end of the day most retirees need money they can get to more than they need a shorter payoff schedule, and a standby line of credit gives you the first one without requiring the second.