The current existing set of classes used to track resharding metrics were originally written with a number of abstractions to allow them to also be reused for global index builds. Later, even more abstractions were added to allow them to be used for online movePrimary. Both of these projects never came to fruition (global index builds were delayed indefinitely and online movePrimary was superseded by moveCollection).

As such, the metrics are massively overengineered and riddled with unnecessary abstractions that make working on resharding more difficult than it needs to be. These should be removed where possible.