I don't understand how the recoveries were negatively impacted from the PFS to BFS. I'm not sure what changed except the companies involved in the work.

When you think about it, improving recoveries has to be right up there near the top of the list of important things to improve any mine value. It is really the easiest way to squeeze more value out of an exploration project.

For example, this work was done by Teck on Highland Valley to extend the mine life:

The mill modernization project progressed in 2012. The project includes the construction of new flotation and pebble-crushing capacity adjacent to the existing circuits, which should increase plant availability and increase copper recovery by 2%, molybdenum recovery by 3% and annual mill throughput by 10% over the remaining life of the mine.