We’re providing two responses to this question given interpretation of the intent. The more likely meaning is related to the confinement reinforcement in the bottom flange. While some owners require confinement bars for the full length of a girder, the LRFD Specifications only require confinement bars at the end regions of the girders.
The second meaning is that side forms require under-ties that pass beneath the soffit forms hold the two side forms in place at the bottom. Top ties are also provided to keep the top of the forms in place. These ties are required for the full length of the girder.