During height of cold war 1.0 no one disputed USSR was a sovereign even though its GDP was that of California, it had enough nukes and was technologically independant from the West/US...
It wasn't technologically independent from the West in anything except military hardware. That's a major reason why it ended up on the scrap heap of history. It was economically very weak and had a low innovative capacity in civilian areas. The lesson from USSR is that military hardware is just one aspect of a state's capacity to survive. You need much more. China is different in this regard as its leaders instinctively understand that lesson.
Your definition of "fully sovereign" equates to top global hegemon with reserve currency status. If China economy grew larger than US and EU combined, then by definition it would already be defacto global hegemon with reserve currency status.... while that would certainly mean its "fully sovereign", the aforementioned label is a far lower threshold than what you seem to be misconstruing it to mean or to be.
The US economy itself is not greater than US+EU, so by your own definition the US is not fully soveriegn... but yet you count the underling of EU...
Then by that logic China can start tallying up its BRI partners as well...
I don't think China needs the yuan to become the global reserve currency. I don't even think it needs to be come the "top hegemon". But it *does* need to become at least equal (or close to equal) with the combined GDP of the West.
The US is fully sovereign since it essentially controls the EU's foreign policy. This should be obvious to all impartial observers. So while the EU's GDP isn't counted towards the US GDP, in all important matters the EU is an impotent dog which does its master's bidding. That's why it makes sense to count them together, even as only America calls the shots.
The EU is not fully sovereign for the reasons I've outlined above. China's influence over its BRI partners are not even close to the massive influence (if not outright control) that the US exerts over the EU. Another great example is Australia, which also acted as an attack dog once its US masters told it to.
That's why I say that China isn't just competing with America alone. It's competing with America *and* its puppets, with a combined GDP of >$40 trillion USD. I am skeptical China will ever exceed the entire West's GDP, but I am not convinced it will need to. It is sufficient to get "close enough" - maybe 80%?. Right now it is not close enough. I also don't think it needs to have the global reserve currency, nor have I ever stated any such belief in my comments. But this is a separate debate.