With restarts, the end and start times of the first simulation and the restarted simulation respectively coincide. This may or may not be desired. For example, this is the behavior one should expected, since the instantaneous diagnostics saved at every step of the output schedule, so this makes sense. However, this makes it annoying to read the diagnostics, since you must postprocess the data to remove this duplicate time value.
With restarts, the end and start times of the first simulation and the restarted simulation respectively coincide. This may or may not be desired. For example, this is the behavior one should expected, since the instantaneous diagnostics saved at every step of the output schedule, so this makes sense. However, this makes it annoying to read the diagnostics, since you must postprocess the data to remove this duplicate time value.