My experience is that Romanian that sounds truly idiomatic to the Romanian ear may often seem redundant to the American ear. Potestasity, do you agree? I think of "am fost aici timp de un an/un an de zile" whereas "am fost aici un an" sounds incomplete, even though by American linguistic logic it sounds fine.
But the Romanian way of thinking is not that this is for emphasis. Rather, it is the most common way of expressing a transitive sentence, it appears. I agree with you on the meaning, but it appears that to leave off the "pe mine" all the time would be almost like leaving off the "pas" in a French negative sentence and just relying on the "ne."