Thanks a lot @xwu for clarifying that.
I am able to see the warning after turning on the other swift flags (-Xfrontend -warn-concurrency -Xfrontend -enable-actor-data-race-checks)
From Sendable-related warnings (SE-0302) backed out of Swift 5.6, it seems that they would continue to refine for Swift 5.7, so is the issue that I pointed out worth the review? (should I leave the bug open for it to be considered or should I close the bug?)