With a paper card, time is of no use as the card itself is the verifying instrument.
With a LOTW QSL, time is a critical factor, in that the time of the QSO must MATCH (plus or minus 30 minutes) between the two LOTW QSLs. The reason for this is the ARRL does not want to encourage "fishing" for the QSO time where either operator recorded the time of QSO incorrectly.
In both paper and LOTW the frequency is not used at all, only the band.
Hope the above clarifies the differences between the two, Paper vs. LOTW QSLs
