The LF should have a better glove due to seeing more opportunities, but does not necessarily need better range. This is how the fielding rec's are set and to be honest it does make some sense to me. Often times (not always) the LF has to cover less ground than the RF. The CF is usually going to be shaded straight away or slightly to the LF side of the bag (again not always but often). In most parks the RF does cover a bit more ground than the LF thus the higher range req't.