Spouting complete bullshit while taking an IELTS test isn't going to lower your final score unless it makes you fumble your expression. In context, "fully and appropriately" doesn't means the ideas are good and the presentation comprehensive. It just means the flow of the bullshit is untrammeled.
I guess some native speakers could have difficulty forming coherent sentences on some of the bigger topics available to us. But the IELTS test usually doesn't go in for the high fallutin kinds of topics. You talk about "everyday" conversation stuff like education, influence of television, leisure activities, the internet, etc. Talking head stuff that wouldn't be out of place at a boring dinner table.
But...
As a part of testing specifically your speaking ability, the IELTS does very obviously ask for three different types of language use. You get questions that want facts as answers, then questions that call assessments, then questions that develop generalizations. The facts are starting points that you provide, the assessments want you to build on these facts and say how things or processes work, and the generalizations want you to abstract away from the current discussion into something more widely applicable.
Which is to say, you, the speaker, are called upon to analyze and evaluate the world around you.
And in China, that's not what individuals are supposed to do. The collective does that. Not you. Individuals in China are supposed to contribute to the collective development of truth and knowledge but the final word won't be yours. Which is fine, I suppose. But what happens if your schooling is built around this idea? What happens if you're so rarely called upon to contribute your own version of the world to the collective understanding that there is no outstanding reason for you to develop the academic version of those skills? You can still speak with the authority and verve of indulged youth in your native language. You can still proffer well known versions of current understandings. You will likely have develop some version of the skills needed to be a contributing member of the collective anyway because in native languages you can't help but pick it up. But then along comes a foreign language in which no one cedes authority to the collective...
What then?