I don't think this answer is correct according to the latest Google Cloud documentation:
If you are migrating from HBase to Bigtable or your application calls the HBase API, use the Bigtable HBase Beam connector (CloudBigtableIO) discussed on this page.
In all other cases, you should use the Bigtable Beam connector (BigtableIO) in conjunction with the Cloud Bigtable client for Java, which works with the Cloud Bigtable APIs. To get started using that connector, see Bigtable Beam connector.