Earlier quoted context omitted.
They may not be paid by the hour, but they're being graded by the hour. It may be beneficial to the company to save overall "company time" at expense of wasting time for many individual employees, but I don't think this analysis accounts for the costs of people leaving or being fired. Both of those are very costly, but they're step changes and hard to attribute to any specific cause.
I've been evaluated half yearly or annually, never hourly that I've known. Do you work in HR?
Think about what the average salaried person (especially outside of tech) might get dinged on either explicitly or implicitly. Come in at 10:00 every day? Not being "seen" enough in your seat or around the office? Not replying quickly enough in Teams/slack? Jira/Github statistics? These are not things that do not reflect a salaried worker's output but you're still getting evaluated by them on an minute by minute, hour by hour, day by ay basis.