Trying to lump "percentage of people in the Upper Middle Class", with "availability of $500" and calling it the economy is absolutely boneheaded.
My wife and I are about $100k a year short of what the article calls "rich", and yet my funds availability has fluctuated from nearly nothing to $80k liquid at any point in time depending solely on my consumerism.
So to call into question the dated surveys isn't asking anything about the economy, per se.
It's asking if the old pattern of consumerism vs. wages still holds true.
Which, just spitballing- it very well might not, simply due to increased interest rates, inflation, and tariffs.
Those things have certainly led me to buy less shit, which has increased my average liquid funds, in spite of no real change in my financial status.
I'm sorry, were you trying to go political with it?