It probably could and in testing it could, they just decided not to find out whether it would really work properly when seven people's lives depended on it working. If you can practically avoid an edge-case you haven't ever relied on in decades before when people's lives depend on it, not risking it doesn't seem that crazy.
Actually, they could but given the fact that the shuttle is not much different to strapping equipment and people to a gigantic bomb they seem to have decided that even though exhaustive testing found no issues a small change in the schedule was less risky.