The leaves are still being fed by the roots via the xylem. It should not be roughed up. The girdle severs the phloem to prevents photosyntate from passing back to the roots. The build up of sugars at the girdle is what starts rooting. If I am certain I will be removing the limb, this is the way I air-layer with the exception that I do not mar the wood underneath and lately I have been using my normal container mix. If I am not sure I want to remove the limb, I do not girdle. If I change my mind later (I haven't yet), I can remove the plastic and growing mix to let the roots dry and wood change back.
For those who are not comfortable girdling in this manner, I have found a vegetable peeler works nicely. It is also useful if you are doing a partial girdle.