Employers can just pay the same amount for 40 hours (paying less for the initial 32 and more for the subsequent 8)

They're going to have a lot of very pissed-off employees when they announce the company-wide pay cuts. And competing employers who instead use the strategy of dropping to 32 hours and hiring more employees to make up the difference are going to be able to pay the full rate without any pay cut, making them more attractive to workers.

Also ... ask yourself, why aren't they already doing this to get 50 or 60 hour work weeks out of their employees? Because it's hard to find employees willing to work below market rate for 60 hours a week. (Most employers already strictly limit employee hours, because they hate paying overtime.)

Now, what you're saying isn't completely insane -- I do recognize that some employers may try to do something similar to what you're saying, while trying to justify the pay cuts as a reaction to the new law. Also, there's nothing forcing them to increase the hourly rate, so for a lot of workers going to 32 hours instead of 40 would be a significant overall income reduction.

There will be some friction, especially at first, but I think that over time, the market will normalize around it, and (essentially) 4-day work weeks could become the norm. It's nothing that hasn't happened before, during the fight for a 40-hour 5-day workweek.