Yes, but as they are saving, they're losing the 5% spread.
Assuming you're starting from a level of normal means, you WILL make more borring at 5 and investing at 10, than taking what would have gone to pay the interest and principal on the 5% and investing that instead, because you're starting from a much smaller basis.
I learned (too) late in life probably, that one borrows on collateral, not take on unsecured debt via borrowing against a depreciating asset. If I have $100, I can borrow say, $50 on very favorable terms and not lose the use of my original $100, all the while building my credit history. I try to cover my borrowing on a dollar for dollar basis, as rates are historically low. Theoretically it is easy to make a little bit of money, sorta like picking up nickels in front of a steamroller. It takes a while, but otoh running up debt is very quick!!! I ran into some credit-card debt problems years ago, student loans, etc., so I try to keep spending more safe.