I have had mixed experience with upgrades to business recently, from guestseat showing on the etihad site yet the upgrade is not working thorugh the site nor by calling the agents as it is not showing in their system. They once explained me that these two categories(business upgrade availabilty and business guest seat availabilty) are different categories. But I am not sure how much to trust them as I managed to upgrade the same flight couple of weeks later. Sometimes the site shows the whole leg Europe-AUH-Australia has a Business Guestseat availability yet the AUH-Australia part on its own doesn't(of course for the very same date/flight). I would like to think that they are playing with the system, the agents are not informed so everybody is tapping in the dark at the moment. Last time I managed to upgrade an eonomy flight to business, with the advertised number of miles. It was late in Jan 2024 for a flight that is in Sept 2024.