It gets the web URL for the file yet uses the file service to load it, so having a sub-path causes it not to be found on disk (the sub-path obviously only means anything for the web server and isn't on disk).
It gets the web URL for the file yet uses the file service to load it, so having a sub-path causes it not to be found on disk (the sub-path obviously only means anything for the web server and isn't on disk).