Widerow inserts are supported for PolyBase hadoop and Datapool tables in SQL Server 2019. However, you will notice that widerow insert to an external table is not supported when the row width is more than 32K.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
To work around this issue, you may change the row width of the table to be less than 32K.