i think it's just that it's not that worth importing? ₹54,999 there right? which is around 820SGD. This is provided you know someone who can buy and bring back for you at RRP. If through 3rd party price might go up? CN set I've seen around 200 less on shopee during sales. Also, local OP13 i think during sales is like 950 give or take a bit? So unless you die die want smaller phone... really not that worth it considering hardware wise, the OP13S isn't even as good as the 13.
Also, possible to flash to global OxygenOS, BUT, like other recent CN OnePlus phones, will have issues. Namely cannot OTA, if not will break signal and camera. So if want update, etc, need to be rooted? or have to reflash every time there's a new update?
This is something OnePlus has been doing for a while now for all their phones by the way. IIRC OP13 CN set also like that?