I'm not very familiar with FUSE or the inner workings of rclone so my assessment could be wrong but it looks to me like rclone uses delete on the backend when deleting folders in a FUSE mount.
This is very slow compared to purge since delete has to go through each file and manually delete it while purge simply moves the target folder to trash. This is of course useful when filtering is needed but in the case of removing a directory, no filtering is done.
Also, I realize that purge is not supported by every remote, so this would have to be a remote-dependent feature.
Please let me know if this feature request makes sense. Again, I'm not very familiar with FUSE, so perhaps the reason this wasn't already implemented was due to restrictions it places.
Maybe you're right. I was hoping FUSE/WinFSP offered some way to get around that. But you're probably right that the OS expects to have to go through each child file to delete a folder.
If someone with more insight into FUSE reads this I'd appreciate your input.