1) Page listing the commands:
https://docs.mongodb.org/manual/reference/command/

dbHash Internal command to support sharding.

The above is wrong, dbhash is used to calculate unique values to compare databases and collections across mongod instances

2) dbhash description
https://docs.mongodb.org/manual/reference/command/dbHash/#dbcmd.dbHash

dbHash is a command that supports config servers and is not part of the stable client facing API.

Not very accurate. It is used primarily for config servers, however it can be used to calculate hashes for any collection or database.