Not always. At a college I worked at the contributions by the school to our health insurance cost was added to employees paychecks as a line item, then the amount of health insurance paid by the employee (a small percentage) subtracted, so the gross salary basically included most of but not all of the schools health contribution. This meant the employee ended up paying some taxes on the schools health contribution I believe. Every other employer I worked for did not show company health insurance contributions on the paycheck stub at all. Maybe this has changed recently (last 20 years?) because applicable laws have changed, or perhaps it only applies to nonprofits or schools?

This had the advantage to the school that employees knew how much of a health benefit they were receiving, employees paychecks looked bigger (until you got to the take home part), and the school paid less taxes (not sure how, but that was the main reason they did it).

It was basically an accounting trick to shift costs to employees, similar to the old trick of giving raises that match inflation; so employees think they are getting raises, and even if they notice the raise only matches inflation (difficult to tell if the business year doesn't match the physical year since official inflation figures for the entire year won't be published till later), what they don't realize is the raise only happens once a year so they are losing to inflation the rest of the year. A very sneaky way to take money away from employees and reduce company costs. I suspect this is part of how USA wages have been held flat for decades.