whether it is 5% or 20% is not really the point Etihad markets itself in many cases as an international airline connecting through Abu Dhabi and as such this offer is too little too late and not relevant to most potential users
I do not know if they have sorted the transfer at Abu Dhabi as I used to get really hacked off as there were no separate premium queues for security when transferring (although there were separate scanners which was pointless if you had to wait in the general queue)