It really depends on the job. For example, security guards need to be present AND vigilant. It’s not reasonable for them to be fooling with spreadsheets on their phone or something. However, a spreadsheet worker is not technically required to sit in their chair 40 hours. They need to get a certain amount of work done. Who cares when they do it? The rub comes when some people think that the spreadsheet job is mandated 40 hours in the chair but it really isn’t. That’s not in the papers you signed. It’s just a “soft expectation” or assumption that management had. If you are completing all the work expected of you during a day, it shouldn’t matter if it took you a full 8 hours or not.

Having said that, someone who only completes what’s given and never contributes extra on their own initiative, or looks for additional ways to be helpful, is not going to be as appreciated. They might not get promoted as fast. But that’s different than cheating.