IS mgr utilizing other usernms regularly

I’m a Network assistant for a 5 site clinic organization. Is it proper for an IS manager to log in as other users and use their usernames as if it were their own when users are away or is this against Networking protocols? If I understand correctly, if an IS mgr needs to view or access certain files on another users desktop, they should have those privileges already set on their username. I think our IS mgr is lacking some serious Network Administrative skills. By the way, we utilize a Winnt 40 and Sco Unix servers with 49 Win98 workstations. Your feedback is appreciated.