Suppose six later students transmit a hadith from the same teacher, while its earlier transmission rests solely on one narrator. The six later branches do not erase that earlier bottleneck; they still share a common basic source.
By contrast, several genuinely independent original paths, each found sound under critical examination, can provide stronger mutual corroboration. That is the evidential importance of turuq mutabayinah, or distinct routes.
Rule: Before treating numerous written chains as independent, investigate common transmitters, possibilities of actual hearing, dependency of narrations, and hidden defects. Multiple chains on paper do not necessarily represent multiple independent attestations.