The design for resharding originally had recipient shards only listening for createIndexes, startIndexBuild, commitIndexBuild, and abortIndexBuild oplog entries from the donor shard owning the MinKey chunk. The donor shard owning the MinKey chunk was chosen to match how mongos forwards listIndexes on sharded collections to the shard which owns the MinKey chunk. Now that resharding will abort the operation if it sees any index being built or dropped, there is no need to special case the MinKey chunk owning donor shard. Removing this special casing would simplify the testing surface area.