Another item to mention is though a runway is the same length from both ends, as far as computing takeoff performance, it may not all be usable. If one end has a smaller than normal safety area off the end, part of the runway may have to be used in computation of the safety area. You then effectively have a "shorter" runway going one way than the other. Along these same lines, the presence and size of EMAS off the end of the runway can do wonders to increase the "length" of the runway in this situation.
Though quite significant at some airports, admittedly, this does not seem to be the case in SAT.