I don't think that this article is a good representation of the debate over these issues and takes an approach where the author seems to have already made up their mind about possible solutions.

This post from Our World in Data probably gives the best overview of stagnation in global poverty

"A generation ago the majority of the world's poorest lived in economies that went on to grow very fast. What is different now is that a rising share of the world's poorest are living in economies which have not achieved economic growth in the recent past.

Half a billion are expected to remain in extreme poverty by 2030 if current trends of economic growth and levels of within-country inequality persist.
The decline of extreme poverty is expected to slow down.

Much of the progress will be driven by economic growth in Asia, and India in particular. The number of people in extreme poverty in Africa is expected to stagnate."

I can't get on to the newint site for some reason so I don't know if they say anything more in support of excluding China, but it doesn't seem reasonable to ignore the progress made in a country that contains ~20% of the world's population. But even if we do that, the progress made at the lower end of the income distribution is still significant, and ignoring it by adopting a higher poverty threshold doesn't make sense to me (bear in mind that there would always be a higher threshold at which progress in poverty would look much weaker, and people suggest different ones all the time).

Of course, the choices about what countries/poverty lines to look at depend on what you are interested in. For instance, if you want to know the impact of global capitalism on poverty, you would not want to exclude China if you think that its rise was largely due to liberalization and trade with developed capitalist economies (I am agnostic about this). My sense of Rosling's main point is that people were/are massively underestimating progress, even at lower poverty thresholds where it should be easier. This is true even if progress at higher thresholds has been less good. Whether Pinker's book is misleading on recent changes in global poverty may depend a lot on how much China's progress can be attributed to 'enlightenment values'.

Also leaving this as a good summary of the debate https://www.cgdev.org/blog/12-things-we-can-agree-about-global-poverty

That is pretty concerning. I would love an explanation of this as well!