So many questions. So little time.
Absent any context to make me think differently, I have no reason to think the two sentences don't mean the same thing. The older employees are, of course, those who are older than the other employees. They are older than the average employee. Perhaps they are close to retirement age. No need to divide the employees into groups by age. Just keep in mind that if they are in their fifties or sixties they are almost certainly the older employees.