If someone owns their home, or has a fixed rate mortgage, then there is nothing to worry about.
I know what you’re saying but I would worry if I was upside down in that home.
Tell that to the millions of (formerly) debt-free German homeowners who were told, in the late 1940s, that - voilà - they suddenly had a 20,000 Deutsche Mark mortgage on their houses, payable to the government!
If cash can be seized, real property and chattel can be seized, too!
Regards,