We are making the DatabaseName::db() private to avoid developers dropping tenant prefix when the tenant prefix is actually required in some use cases. But, there still are some use cases in which tenant prefix is not required, for example:

• the OpMsgRequest should has non prefixed db name if there is "$tenant" in msg body.
• the change stream events.
• the internal created BSON object for parsing command request with IDLParserContext and known tenant id.
• document source lookup output.