In short, the fining agents benefit from sediment in that it allows them begin more vigorously and form larger particles, which can easly fall out of solution. Fining may stall without suitable sediment. Here's a statement from WE:
The clearing or fining agents used in Winexpert's wine kits, whether chitosan or isinglass, both act more efficiently in clearing wine when they have a base of sediment to begin with. The sediment acts as a trigger mechanism that sets the finings into action, clearing out the mix of proteins, pigments, phenolics, dead yeast, etc.
Both the fining agents and the particles they need to clear from the wine have either a positive or a negative charge. A negatively charged fining agent like bentonite will serve to bring together those particles having a positive charge, while positively charged fining agents like chitosan or isinglass will attract negatively charged particles. This process allows for the molecular weight structures of the particles to become larger: smaller particles join together to become larger particles, which in turn fall to the bottom of the carboy when their mass becomes great enough.
If the fining agents do not 'find' enough particles in the wine must that they can join together into larger particles, the clearing process may stall: there will not be enough small particles present to conglomerate into the larger particles which will fall out. Small particles on their own will remain suspended in the must, meaning that the fining's efficiency is reduced. In other words, the wine won’t clear as well or as quickly.
This is why you must thoroughly stir the sediment when adding package #4, as it effectively mixes the fining agents and the particles together to start the clearing process. Resist the urge to transfer or rack the wine. Stirring up the sediment will facilitate the clearing process – not hinder it.
I believe, however, that you should be fine although clearing could take considerably longer.