Bi Engine with BigQuery Materialized View not working

[finderco-engr]

We have a BigQuery Materialized View with:

• allow_non_incremental_definition set to TRUE
• 2 CTEs
• a window function
• a few left joins
• the MV and all base tables are added a preferred tables in a BI Engine reservation

BI Engine docs clearly state materialized views are supported and we're in line with the limitations.  While the docs are a little inconsistent around join support (MV docs say left joins aren't supported, but this Google blog says they are) this MV is allowed to be created with non-incremental option. I've waited at least an hour for any BI Engine config changes to settle.

However, when adding the MV as a Looker Studio data source and then exploring or using in a Looker Report, the BI Engine is not working for this materialized view.

Not Accelerated by BigQuery BI Engine

This data source connects to a BigQuery view. Looker Studio BI engine doesn’t currently support materialized views.

What do we need to do to get more information or get this working?