Yeah, there must be a good reason, I just find it odd that they're adding extra weight for a weapon that is pretty much mostly for show.
That depends how you look at air combat. The Chinese may well feel that if their AAMs are not abl to engage US aircraft in the face of ECM and so on, that whonking things with a cannon is pretty smart. That delta tail should make the turning circle superior to an F-14/F-16. Or rather, I'd imagine it would.
It's also entirely possible that someone at NORINCO is just an old fart and wanted twin guns. Let's not forget that however smart they are they are pretty corrupt and muddled management wise.
Also, Steve is quite correct, as of earlier this year China is legally obliged to declare war if Taiwan asserts independence. Indeed, it may not have to declare it. I think it automatically goes into effect. My own feeling is that China will try to bully Taiwan into rescinding all hope of independence, by threat of force. However, depending on the USA and how jaunty tehir pilots are feeling they may execute landings. All the USA has available at short notice is one carrier group (www.globalsecurity.org).