That report junk feature doesn’t do anything much. It only sends Apple the report, not your carrier. You will notice it also only appears on some messages - I think contacts that have not messaged you before.
To report people properly and actually improve the messaging experience for everyone, you have to follow the steps I mentioned in my other comment: https://news.ycombinator.com/item?id=41704119
> It only sends Apple the report, not your carrier.
Depending on your carrier and country or region, reporting spam you receive with SMS, MMS, or RCS shares this information with your carrier and its affiliates.
https://support.apple.com/en-sg/guide/iphone/iph203ab0be4/io...