I've actually got to make a point in Rifter's favor here-
In a later spoiler mission, they manage to make it where the enemies don't move until they see you. That could've been done here as well, noticing you, the reinforcements advance, since they think you have spotted their trap that they were going to destroy your only normal escape.
In a later spoiler mission, they manage to make it where the enemies don't move until they see you. That could've been done here as well, noticing you, the reinforcements advance, since they think you have spotted their trap that they were going to destroy your only normal escape.