When Grant toured his divisions during the morning he told Prentiss to hold the Sunken Road to the last man. Prentiss followed these orders completely. He did not try to get out of there until he was flanked on both sides. Very few of his men got away as the Confederates closed in from all sides.
Prentiss could have pulled his men out earlier. The most logical time to leave was probably when Hurlbut retreated from his left flank. This happened at a time when the fighting in his front had diminished so it probably appeared that he was safe until reports of the retreat on the left became known.
If Prentiss had pulled his men out when Hurlbut did he might have been able to prevent the capture of roughly 2300 Union soldiers. This may have allowed the Confederates to make a more coordinated assault on the Dill Branch line as historically they lost some of their manpower to gathering up prisoners. Of course the Dill Branch would also have been stronger by those 2300 men.
Prentiss’ staying in position until the bitter end did cause the capture of a large number of Union soldiers but it also delayed the Confederate attack on Dill Branch by at least a half hour. It is debatable if the Dill Branch line could be breached but giving the Confederates more time to try it would not be a good thing. It is a critical decision because it cost the Confederates valuable daylight, which at this point was worth more than manpower.