The backup is precautionary. Just in case there is something on your server that conflicts, or a file that is corrupted while uploading, or some unknown event. You should always be ready to put everything back if something unexpected happens.
Upgrading from 1.1.2 to 1.1.4 only requires that you replace some of the files in your current installation with files in the upgrade package. There are also a few new files.
There is a lot less that can go wrong upgrading from 1.1.x to 1.1.4 then from 1.0 to 1.1 (which makes database changes).