"these people are not millionaires in any sense"
Uh, assuming their houses are mostly paid off, actually they are millionaires, based on the commonly used definition:
a person whose assets are worth one million dollars or more
More interesting information:
As of Apr 12, 2023, the average annual pay for the Millionaire jobs category in the United States is $76,071 a year, or approximately $36.57 an hour.
and,
The nearly 22 million Americans with a net worth of over $1,000,000, account for 8.8% of the country’s adult population and over 39% of millionaires worldwide. Feb 24, 2023
Of course, as you observed, being a millionaire based on assets is different from having a million dollars.