If I understand correctly you are talking about what is called reworking chocolate.
Using chocolate as an ingredient to make another batch of chocolate.
In all factories chocolate batches fail from time to time (gritty, sandy or too low viscosity) and there are various methods for reworking the product.
All of them require calculations so finished product has the same composition as intended and lecithin content must be taken into consideration.
We use conches to make chocolate and to achieve best results we add ~0.05% lecithin at the very beginning and 0.2-0.3% at the end just before final cocoa butter additions. With final content about 0.3%. This gives us the best conching profiles.
Taking above into consideration my rework recipe uses failed batch (which already contains 0.3% lecithin) at 10% of the mixer recipe with no additional lecithin added and other ingredients adjusted. Mix gets processed in the refiners and loaded into the conche. This means that I will start with less than 0.05% of lecithin in the conche.
To sum up.
Chocolate can be reworked but only as a small part of new batch if one seeks consistency.