AWS Glue Spark ETL writing to S3 wont trigger S3 Events

I have a few Glue Spark ETL jobs that extract and transform data from a RDS instance to a S3 Buckets. No problems here. In these buckets, I've set up events configured to trigger Lambda functions on All object create events, All object delete events, but the ELT does not trigger the events.

Something triggers ETL -> ETL reads/transforms data -> ETL Writes to S3 -> S3 Event triggers Lambda

                                                                         /\
                                              Works fine until here.         Event does not happen.       

All searches I've made point to triggering ETL with S3 events, not the opposite. Why would this not trigger an event, when the interaction with the CLI do ?

Note: the RDS and the ETL jobs are being run in an AWS account different from the account where the buckets are. I don't expect this to impact the events.