Could inflation be a driver of these numbers (wage and spending growth for lower and middle households vs high) growing in tandem? Didn't see that mentioned in the article
I believe the data strongly suggests structural demographics is driving up wages, with the labor component being somewhat inflationary (depending on vertical/industry). The labor market is resilient because (as of this comment) ~4M Boomers retire a year, ~11k/day, ~2M people 55+ die every year, about half of which are in the labor force; that means ~13k-14k workers leave the labor force every day in the US, ~400k/month.