I'm not sure what "gaps" you're talking about in regards to the Indus Valley civilizations. I referenced them once or twice, and basically just said they were considerably older than anything that could be considered "Chinese," which is true.

The question is about Bronze Age civilizations in modern China and my answer was about such, it was not meant to provide a comprehensive history of Indus Valley civilizations. If you re-read the post, you will see that all specific date references I mention are regarding Chinese civilization.

I'm not sure how there can be "gaps" in something when it's not the topic of discussion, or particularly relevant to such outside of tangential comparison (like I did).