Well wasn't this gang of 600 hand picked from 22 different battalions? Presumably for their hand to hand combat prowess?
The problem with that sort of mixed unit is lack of unit cohesion and morale. You can in the video the front of the formation is already in action against the PLA while there are heaps of people standing around in the back looking lost. This also went a long way to diminish the initial numerical superiority.
To be fair this was before the actual combat happened. But I agree with your points. Indian numeric superiority actually proved to be its undoing when the tide of battle turned. In pre-gunpowder warfare, most of the injuries and deaths are not inflicted by blades and arrows, but stampeding troops.
The use of so many hand picked soldiers from different unit seems to be a bad move. India is diverse country with many different languages, many not intelligible to one another. That could prevent serious communication barriers during combat. The commander in charge is also probably not familiar with troops from different units.
Finally, there does not seem to be a clear line of command succession in the Indian army. When their commanding officer is killed or captured the rest of them don’t know what to do. I think they probably expected something similar from the PLA, which prompted them to perform a “decapitation strike” against Commander Qi and Officer Chen. I think they genuinely expected the rest of Qi’s battalion to scatter and flee so they can capture it all on video and get a big fat promotion. The irony is that those who lived (even the captives) all got rewarded despite their failure.