为什么Cloud Dataflow在与我的数据所在的不同区域运行其工作人员？

In an evaluation of GCP as a potential analytics platform for our business, I have set up a Cloud Storage bucket to be located in the EU. I have configured my BigQuery dataset to also be located in the EU. But when I run an ETL job in the Cloud Dataflow service that moves data from the former to the latter, I see the following message in the logs:In an evaluation of GCP as a potential analytic