I'll first point out that this is a pretty semantic argument we're having, and it's a pretty frivolous argument we're having but I like frivolous arguments We both agree that Taiwan is autonomous, but where we differ is whether autonomy makes Taiwan a "real nation". Lets break down the quoted definition for a sec:
Yes, Taiwan does have a centralized government.
Only de facto sovereignty, not de jure sovereignty.
Yes, Taiwan meets these criteria.
Mostly informal relations. Taiwan is incapable of even establishing a formal embassy in the U.S. and other Western countries.
Taiwan can't even officially declare independence without China shooting missiles at the island. When the U.S. colonies declared independence, they fought a war against Britain to obtain it. Taiwan hasn't done that yet, or worked out a diplomatic solution.
And that really is the crux of my argument. When Nixon and Kissinger pulled the ultimate real-politik move by forming a tact anti-Soviet alliance with China, the price to be paid was throwing Taiwan under the bus.
Ghana can strut its independence all it wants, Ethiopia can too, so can Sri Lanka. Taiwan can't, unless it's ready for war. Taiwan can't even get formal embassies with most countries. Those two are two major sticking points that prevents Taiwan from being a "real nation".