What made them make that decision? Was it like "lets be as precise as we can because we want to get to the spot X because X is special" and thus "Lets let the software always compensate for any errors to get to X". I am assuming that even at this point they tested the software for extreme conditions. It is most likely that once this assumption was made the Software was built that way, i.e: "Lets test the Software can always correct for any issues to get to X with feedback(like thrust)". It trades off Safety for Accuracy(to hit X).
This time the idea was "Lets select a trajectory to X" but this time "We will let the software prioritize safety(altitude, speed and heading) to be within norm once we start descending towards X". And additionally "Not make any corrections if we are somehow too far off X if it exceeds safety limits". It trades off Accuracy(to hit X) for Safety.