The Work Ethic is for the image of working, rather than actual work for the most part.
Most employees will show up 15-20 minutes early for work, even if they don't have extra work to do, because showing up early gives the image of being a hard worker. Most employees will stay late until the boss leaves, even if they don't have any work, this gives the image of being a hard worker. This applies mostly to office jobs, as it's not as easy to feign effort when it comes to manual labour.
Let me give some examples. When making my schedule at the city office, my coworker was trying to distribute my time evenly across schools according to how many classes they had within that school versus days of the month. The math really isn't that complicated, and in the West, someone would just make an Excel spreadsheet to do it automatically if you punched in how many days of work there were in a month, semester, or whatever.
But my coworker was grueling over this simple math for about 1.5 hours, constantly talking to herself, and making it seem like it was an impossible job, because she had nothing else to do, and had to be there for 10 hours, so she wanted to keep looking busy as long as possible, even if the effort wasn't legitimate. She demanded that she'd have to recheck my work after I did it for her in 5 minutes.
This is the source of 窶愿??堙ｨﾅ陳ｾ (hitorigoto -- self-talking). This is why you get people shouting 窶堙ｦ窶堙≫?堋ｵ (yossh!) after they finish a task. It's not any source of personal satisfaction most of the time, but rather the indication to everyone else that they put some effort in. Same thing behind the people who talk to themselves mid-task.
This is why you see teachers taking 20 minutes to get themselves tea or coffee, while doing the fake feet-shuffling run. Because it makes them look busy, even if they're just getting coffee.
There's nothing efficient about that. There's no real work ethic about that. It's an ethic about looking like you're working more than anything. At the company I was employed at before Japan (a printer software company), the hours were very flexible, and people would work 6 hour days sometimes. But for those 6 hour days they wouldn't take lunch, they wouldn't take breaks, and they wouldn't screw around on the internet like the rest of us mere mortal employees. So while it may look crappy that they're getting into work at 11am, it certainly didn't affect their work ethic or productivity. It only hurt their chances for promotion (because while that works for an engineer, managers need to work longer hours to deal with problems that come up with their projects).
I guess it depends on the type of work. The effort put into the service industry is far more genuine than the effort put into the office/salaried-worker fields. The former is far harder to fake (though you'll see people in the service industry wiping down random services at the supermarket, or standing at a random counter with no customers when the registers have 20 minute lines at them). It seems busy in an office until you actually pay attention to what people are doing, then you realize that the long hours are just a front for extreme slackerdom otherwise.