Really? I don't know all the details, but with fine weather forecast at destination, no expected ATC delays and enough fuel for an alternate such as Macau, would you really divert to an enroute alternate to top up the tanks?
Even if they were running low on fuel at the end of an ULH flight and had to drop the alternate, I'd suggest it would be perfectly reasonable to continue to destination if the forecast & actual weather was fine and there were no expected delays. If you then throw in an ATC delay followed by a go-around then it is not at all surprising they had to call low fuel.
Call me old school, but I don't think I would start my Take Off for a LR Flight with an alternate, which is a stone throw away from my destination. Especially for a sub-tropical destination during a summer day and given the "strange" air space arrangement in HK.
Even if the unfortunate crew encountered some unlucky circumstances during their flight, I find the idea that a Widebody Aircraft had to do a 180 on a go-around agains the traffic and came close to another aircraft, really really uncomfortable.
Without wanting to start a fight or finger pointing, I just sincerely hope that CX and KA start to look into their fuel policy and chose a maybe slightly more conservative (and given the event described above) a
safer alternate. Just like many other airlines do.