Photo Credit To Andrew Yee
It is not restricted to workplaces and is the reason you would most likely see people in public places find a snug spot and hit the snooze button, or on trains, no matter how crowded, and even in restaurants. The unwritten rule? Sleep compactly, without violating spatial norms. So yes, the salary man splayed out on the train floor will be reproached for being socially disruptive and this would not be considered inemuri.
One of the reasons public sleeping is so common in Japan is due to the fact that most Japanese adults get little sleep at home, a 2015 government research showing 39.5% of them sleep less than 6hours a night. Whether or not this habit will continue is debatable as smartphones nowadays have a way of transporting people, both young and old to a different world with their eyes wide open.