It's a good question. If what I proposed isn't it (PLA's Korean experience) then what was it?
I didn't deny the relevance of the immediate prior experience in Korea, the long, hard grinding during the Civil War and the war against the Japanese. I was highlighting the similarity between the earlier mountain warfare that the old Indian Army was familiar with, and the mountain warfare in which they found themselves.
First question, was there a similarity? Should we look closely at the Afghan campaigns?
Second, which were the units? Did they all go to Pakistan at partition?
Third, was there too long a gap? When was the last engagement on the north-west frontier? Were those veterans retired?
Fourth, what were the units engaged on the Indian side? What was their battle experience during the previous couple of decades?
Fifth, PLA tactics in Korea have been very well-reported - a war of movement, all the time, of marching separately, very Napoleonic, and in Korea in Napoleonic numbers as well; mind-numbing superiority was achieved.
These numbers were not used in exclusively frontal attacks, although those were used as well; on the contrary, the more frequent method was to outflank UN troops using rough ground, going off-road wherever possible, attacking UN troops on their flanks, rolling them up with these flank attacks.
And when these UN forces disengaged and retreated, they found that the PLA had overwhelmed guard units, including military policemen, and were dug in, on slopes overlooking the lines of retreat, with heavy machine gun concentrations enfilading the line of retreat.
Does this match what Indian survivors reported?
All this at the battlefield, at the tactical level. There are other, similar questions at the strategic, at the theatre level, but these have been addressed before; it is the tactical level questions which remained slightly obscure, perhaps due to embarrassment. After all,
the story put out for popular consumption (this is a hypothetical construct, there was no concerted bid to manufacture one, no black propaganda effort) did not talk about masterly tactics of the PLA on the battlefield, the deception practised, fires left burning on a forward slope of a hillside in view, unit marching quietly on a night march past the Indian positions to take up positions
behind the Indian trenches and bunkers.
They did not talk about the night attacks after a buildup of preliminary noise and bugle calls, about extreme edges of trenches being attacked by the PLA in full strength, and rolling up the entrenched Indian formations.
Coming to your summary:
Could it be initiative and scale? The PLA had a battle plan going in and their forces moved as a whole and in concert while each group of Indian outposts was left to act on its own, out of support range of the other brigades. In short PLA active, IA reactive.
Indeed, it could. The decision to take the initiative was key, scale perhaps was not a factor, but integration was. Each PLA unit knew what it was doing, and what the others were doing, and why - their battle plan, as you put it, was up and running, their forces moved 'as a whole and in concert', while Indian formations were isolated, on their own, out of support range.
This is straight out of Mao Ze Dong - On Warfare. There Mao adapts Sun Tzu to guerrilla warfare. The principles are laid out in clear and lucid order, analogies hammered in until the meanest intelligence could grasp it, and it was reiterated until it begins to hurt - movement, movement, movement. And against that, B. M. Kaul's damned positional obsession.
There are many more questions, but let us ask all this progressively, as we go along, and it is hoped as others also contribute: Popeye must be straining at the leash!