I'm no sociologist, but certainly it's true that the ideas in these philosophies are very different from Descartes' mind/matter dualism or other such Western metaphysical ideas which support the individualistic beliefs in the West. However not demonstrating the same individualistic values does not mean therefore adhering to some other vaguely defined set of collectivist values. If anything, most of the philosophical thought over this time (which we group together despite the fact it ranges over centuries) reflected the political disunity of China and therefore spoke more to the need for structure and order. Obviously one way such order can be realized is in a more collectivist way of thinking, and there are such ideas in classical writing (famously, https://en.m.wikipedia.org/wiki/The_Foolish_Old_Man_Removes_the_Mountains). Overall, however I am not convinced that Chinese culture is as uniquely collectivist as the China watchers like to say, it is merely not individualist. A parallel question would be, why is the West not as collectivist despite such values being so strong in the Bible/New Testament (love thy neighbor as thyself, give up everything to follow me, etc.). These questions are not clear cut.