Translation mistake (?) in Mary Beard’s new Emperor of Rome

Salvete! I’m reading Mary Beard’s new book (which I like very much) and I stumbled over her translation of the first sentence in Tacitus’ Annals: Mary Beard translates the perfect form "habuere" into present perfect "has been ruled" (I don’t mind the passive here). As I’m not a native speaker of English (but German) I am puzzled by this present perfect; at first glance her translation seems like a mistake (I expected simple past) but considering the fact that she’s a classicist I’m afraid the reason for her using present perfect is a bit more sinister if not dishonest. Please judge yourself!