Earlier I had observed this type of case last year. Due to the Fog the train was cancelled. So the passenger not traveled to his destination but He had booking of return journey in Tatkal Quota.
I filed TDR for the return journey but it was not approved due to tatkal quota & I talked to the customer care of IRCTC that passenger was not traveled due to his connecting train cancellation so he should get full refund but they rejected my point.