You may be stoked to put it though the mill because you don't...

You may be stoked to put it though the mill because you don't have to drill and blast it . You may be less stoked when the recovery is lower then fresh rock. Particularity since the easy to float stuff has already been separated and taken. A metallurgist will tell you that. (Actually the geo's and mining engineers may too).

Further your not adding the tailings to the fresh rock you're adding the fresh rock to the tailings. The a latter is in the majority.
BTW that's why the DFS report was important to understand.

Further as a miner you will know how problems in mining can occur and you can easily get behind schedule.
God willing you don't have rock falls. Seismic activity. Water ingress etc. apart from losing the seam.