The illustration shows a neutral brought to the panel.Not everything has a neutral. If all loads are 3 phase or line to line you don’t need it. Motor circuits for instance don’t need it. Heating sometimes. Lighting is better if you use a tranny anyways.
The line that they are trying to depict from the center point of the Y connection to the terminal block as a bonding jumper would actually be the neutral in this scenario.
Not just a jumper