I am just theorizing here; have not used the process. Might this be for a roller transport without washes between developer, bleach and fix? So there could be carry over that the replnisher is expecting to conteract to maintain the right pH to work best. With no residual carry over when the tansk are freesh, a starter might be needed to 'muddy the waters'?
I ancecdotally recall that the bleach in some P processes was strongly acidic,and that the used developer (alkaline) was held back to mix and neutralize the bleach prior to disposal.
Hope this helps others to think of why the starter is needed here.