For reference,

% rclone sync -vv r2-bucket:dumps ./tests/dumps
DEBUG : rclone: Version "v1.62.2" starting with parameters ["rclone" "sync" "-vv" "r2-bucket:dumps" "./tests/dumps"]
DEBUG : Creating backend with remote "r2-bucket:dumps"
DEBUG : Using config file from "/<user-name>/.config/rclone/rclone.conf"
DEBUG : Resolving service "s3" region "us-east-1"
DEBUG : Creating backend with remote "./tests/dumps"
DEBUG : fs cache: renaming cache item "./tests/dumps" to be canonical "<path>"
DEBUG : Local file system at <local-path>/dumps: Waiting for checks to finish
DEBUG : Local file system at <local-path>/dumps: Waiting for transfers to finish
DEBUG : Waiting for deletions to finish
INFO  : There was nothing to transfer
INFO  : 
Transferred:              0 B / 0 B, -, 0 B/s, ETA -
Elapsed time:         0.2s

But I can confirm there are files in R2 interface, and the local spaces dumps/ are emptied.