"Exclude folders" and "Exclude files" work differently:
If I click on "Exclude folders" and specify e.g. /temp, I get the message "/temp is not located within your home directory. Not added." -> Correct.
But in case of "Exclude files" I don't get any message if I specify a file out of my home directory, it is just added.
Of course this doesn't make any problem from the point of view of the functionality, but a little bit inconsistent.