Resharding uses SamplingBasedSplitPolicy, which is a descendant of the regular InitialSplitSpolicy base class.

The function calculateHashedSplitPoints defined on the parent is only used in other child classes
(SplitPointsBasedSplitPolicy::SplitPointsBasedSplitPolicy and AbstractTagsBasedSplitPolicy). The SamplingBasedSplitPolicy does not rely on this method based on the code inspection.

If the shard key consists of only a hashed field we do not need to sample and can split the space deterministically among the recipients. This allows us to mitigate known issues with the $sample implementation and allow the final distribution of chunks to mirror the distribution of the customer's data without the downsides of sampling.