Good catch on purge as I don't use it personally so thanks!
If his goal is to remove a folder based on backups, he does not want to use 30 days on delete as that will remove all files everywhere.
I'd use purge but you'd need to get a bit savvy and create a list of directories to delete.
felix@serenity:~ rclone ls GD:testing
213 hosts
243 delete/hosts
243 2/hosts
243 3/hosts
felix@serenity:~ rclone purge GD:testing/delete
felix@serenity:~ rclone lsl GD:testing
213 2019-07-01 19:56:08.748000000 hosts
243 2019-07-09 15:28:26.432000000 2/hosts
243 2019-07-09 15:28:30.502000000 3/hosts