The boomers have more invested in the houses so more to lose. Having a home paid off just means even more money invested in your home, not less. Gen X and y will be hurt but not as much because defaulting on a loan will mean the liability goes back to the bank. Strategic default has been a thing since Britain abolished debtors prisons, and if you lose enough value in something you don't own there's always the option to walk away. If you own your house you absorb 100% of the loss of your asset with no way out.
The banks will be forced to make concessions to those with mortgages or face 100% of the value loss on their own balance sheets, so the effect on those who don't completely own their property will be muted and shared between with the lenders