So I read the full text of linked law about this - and it makes exactly zero mention about discussing pay. The closest I could find is you can't forbid people from discussing unions.
1. https://www.govdocs.com/can-employees-discuss-pay-salaries/
Telling employees they can't discuss pay pretty much directly leads to them not being able to assist each other in getting better terms of employment.
There's also a difference between directing employees to not discuss certain matters during work hours and stating that they can't discuss their pay with other people...