Incrementing reshardingStatistics.resharding.opcounters.insert is technically redundant with shardingStatistics.resharding.documentsCopied but the opcounters version allows the graph to be continuous as the recipient shard transitions from cloning to applying.

https://github.com/mongodb/mongo/blob/9103cc7b17be65b107ab7c9d49ce111bb32654fc/src/mongo/db/s/resharding/resharding_collection_cloner.cpp#L314