Sixth Tone isn't directed at the Chinese market though, getting blocked by the government shouldn't be a problem for them, as SCMP proves. The difference is that SCMP is owned by Alibaba, while Sixth Tone is part of the Shanghai United Media Group, who are controlled by the party committee of Shanghai. The journalists might not think of their work as anything bad (宣传 doesn't have a negative connotation in Chinese, after all) and I don't think they'll publish outright lies, but they wouldn't exist if not to influence public opinion by countering the usually negative reporting on China with a more positive spin.

That doesn't mean I advise against reading them (I did say that they publish high-quality articles, after all) but you need to be aware that they're not going to tell the whole truth.