Why has China's integration into the global economy caused it to slow it's output? In the following passage, what does it mean to be integrated into the economy and why does this mean that now China and India are integrated into the economy that their output has slowed down?

In the 1990s and early 200s, global commerce was growing at twice the
rate of output because big economies such as China, India and in
eastern Europe were being integrated into the global economy. Now they
have been more or less absorbed, it is only natural that things slow
down, but this does not mean we have reached the high-water mark, says
Okonjo-Iweala.

Ref: https://www.google.com/amp/s/amp.ft.com/content/87cb4674-6db7-41cf-a82e-44b83eaa436c
Being integrated into the global economy means that country increases its trade openness and lifts restrictions on capital flows (you can look at this paper).
The article does not say that China's output slowed down. It says its rate of growth slowed down. Usually, a country that used to be closed and did not trade much before experiences a boost in the rate of economic growth. This is because trading allows the country to specialize in a good where the country has a comparative advantage. This boosts growth by a lot at the beginning but the effect eventually wears down as the country gets fully specialized and all low hanging fruit was already picked.