sqlos.process_killed Extended event not firing on SQL 2019 Enterprise

I have an extended events session configured, trying to determine the T-SQL of the process being killed. But this event seems to never fire as I monitor the session in real-time, despite the fact that SQL Server Log definitely shows multiple SPIDs being killed.  Can anyone suggest what I am doing wrong here?

CREATE EVENT SESSION [Killed] ON SERVER 
ADD EVENT sqlos.process_killed(
    ACTION(sqlserver.database_name,sqlserver.session_id,sqlserver.sql_text,sqlserver.username))
WITH (MAX_MEMORY=4096 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=30 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=NONE,TRACK_CAUSALITY=OFF,STARTUP_STATE=ON)
GO