I think there is a real world space separating people in work experience.
I've never worked a job where 40hrs was even enough, so any efficiency is instantly absorbed. That is the work world as I see it.
However I've run into in people online and in real life whom's entire work life seems to be on the opposite side. It seems to be a rather large swath of people as well. They have never worked anywhere where they even have 40hrs of work a week to be done.
Even last year I ran into a guy who gets paid 140k to by his own admission(12+yrs), to basically update a handful of websites a few times a week(shockingly...he is concerned about ai taking his job). Those jobs are not coming back and those that exist are rapidly drying up. Thats the disconnect. There are in a national sense a large number of people that have literally never worked an actual job even though they went into an office their whole working life, and everything about their life outside all reflect that they have worked a job despite never having done so. Those people are in for some tough times.
In my experience, at some places you can also have both: a job where during some weeks there is little to do, but you have to spend 40 hours sitting in the office regardless, and during some weeks there is so much to do that you need to work overtime. You need to be flexible, you see, but the flexibility only goes one way.