The Sages were concerned that individuals would plant vegetables in the seventh year and claim that these had grown by themselves. They therefore forbade consumption of Shemitta vegetables where the planting may have been during the Shemitta year itself. The date that this restriction starts depends on the type of vegetable and how long it takes to grow. this is known as Sefichin.
Otzar Beis Din is a representative of the public interest by hiring people to pick and transport the produce to a distribution center near the consumer. paying them wage appropriate to his significant skills and experience in knowing how to manage this operation. the money does not go to towards the produce, rather to the workers effort in collecting, thus mitigating the concern for using shmita produce in commerce. This is all legitimate use of an otzar beis din.
Is there an issur of Sefichin regarding produce bought through Otzar Beis Din? how can we know that the landowner is not working on the field, but claiming it grew wild, Does Otzar Beis Din also mitigate the issue of Sefichin? Is that fact that the field is under the auspices of the Otzar Beis Din enough of a reason to assume that the farmer isn't working on the field?