I find the belief that 4-day work weeks are broadly supported / feasible to be a bit of the typical tech-world conceit.

If you imagine this being applied to everything in the corporate/services world (and work is not "divisible"), would you be happy to have businesses closed 1 additional day per week? The DMV closed on Mondays -- but the fees and pay of employees remain the same? How about if prices go up by 20% to pay for the cost of having a 4 day week? Your plumber or car mechanic or doctor having 20% fewer available times to see you?

The idea of the 4 day work week where people can do all that they do now, but be more efficient about it in 4 days instead, is something exclusively a privilege that white collar workers can even consider.