The Driver CRUD API spec was implemented in the mongo shell as part of SERVER-17953. The Driver CRUD API spec recommends deprecating the bulk API if the driver already implemented it.

Q: Didn't we just build a bulk API?

Yes, most drivers did just build out a bulk API (fluent-bulk-api). While unfortunate, we felt it better to have the bulk api be consistent with the rest of the methods in the CRUD family of operations. However, the fluent-bulk-api is still able to be used as this change is non-backwards breaking. Any driver which implemented the fluent bulk API should deprecate it and drivers that have not built it should not do so.

Note: The implementation of the Driver CRUD API spec in the mongo shell (crud_api.js) uses the code for the bulk API (bulk_api.js) for executing operations, as does DBCollection.prototype.insert(), DBCollection.prototype.update(), and DBCollection.prototype.remove() when the mongo shell's write mode isn't "legacy".