According to some recent data[0], 22% of households earning above $250k report themselves as living paycheck to paycheck. That alone tells me that the term can have very different meanings for different people. Perhaps those high earners mean that after all the taxes, retirement and ESPP deductions are taken out of their paycheck, what's left over is just enough to pay for their lifestyle. That's not what I would call paycheck-to-paycheck. And whatever the definition, I can assure you that 22% of the households in that income bracket are not a paycheck away from homelessness.
[0] https://www.lambdafin.com/articles/percent-of-americans-livi...