I don't think that was the previous behavior unless I'm reading this wrong, but was that the intent?

Looking at line 251 below the old behavior was (paraphrasing):
globStatus(path).exists { x => x.name == "_SUCCESS" } // so looking for at least one file named _SUCCESS returned from the glob

and the new behavior is 
globStatus(path, SuccessFileFilter).length > 0 // no need for a call to exists(), all files returned here are named _SUCCESS

(note that the .map is just unboxing an Option, not maping over a List[List[]]

Once again, this method can't really guarantee that you've got all the required _SUCCESS files, for example if you pass in "x/y/z/2014/" it's not going to tell  you hey x/y/z/2014/07/19/00 is missing a _SUCCESS file.