My dad says if China, Nepal and BD cutoff at chicken neck it won't work. I never believed him.
the thing is they will try all conventional routes to enter Indian territory and also the non conventional. They may gain at somewhere but then McMahon line is long India can infiltrate any where on that.
Doing that near Sikkim is more advantageous because then Lhasa is just few hundred kilometres away, thats why Chinese concentration will be more in that region.
Where as water bodies are more near Aksai Chin.
So when one says China will try to cut off, well they can cut off but then counter attack will cut their strike force as they will be too much away from HQ and base.
Even capturing a post requires cold start , like within 10 hours they will have to engage otherwise it's game over for them.