The Question

These explanations seem to contradict one another. The implication of the second explanation is that if the previous family would allow the current family to advance their offering to Friday, then that would be permissible. It is only because we assume that the previous family does not want its time cut short that we defer the current family’s offering to Sunday. But Rashi’s first explanation (in Megillah) implies that under no circumstances can the family advance their offering to Friday, because their obligation has not yet begun.