The auto filter factory I work at also has those posters, new in the last couple weeks. They don't give us a specific time, or time at all, to do them, but want us to do them at the line - between parts! As the lines are set up to run as fast as the machines can run, we really don't have spare time, nobody is going to waste their breaks for exercises, and most of us get enough motion just doing the work.
If we had desk jobs, or otherwise remained largely motionless, they might be useful.
I think this is related to their new decree that wristwatches are "jewelry", and therefore a safety hazard. If your watch gets caught in one of our machines, your arm is already being chewed on, so it isn't likely to be a big hazard.