China is as much a SA nation as india is, China has borders with Afghanistan, Pakistan, nepal, india, Bhutan and myanmar. The only nations that it has no direct borders are Bangladesh and maldives, so if myanmar can join why cant China? China has a huge market, a lot to offer to give some life into this dying group and can bring balance.
And India has borders with myanmar,china,Afg (theoretically on paper according to Indian claims),pakistan(with many pakistanis seeing themselves as more ME/Central asian than south asian).So I guess India is a part of SEA,EA,CA and ME all at once?
Or the nations to the northern tip of South america as they are so close to North America that they are North American than south american?
Or china has borders with so many ASEAN nations that it is a part of SEA effectively?China has borders with CAR so it is now a central Asian republic to boot as well?
The former USSR or Russian empire before was a part of europe, Middle east,East asia,north america all at once as it shared borders or had some territories in these parts?
Even most of NE is not really South asian per se but South east asian in case of most NE with South tibet or sikkim being a part of tibetan spehere of influence and ultimately Chinese.The only one sticking out being Assam which is mixed of South asian,some mongoloid from China and Burma.
Some kind of absurd logic that is,sharing borders doesn't mean one is part of a particular regional classification/group.China is what defines east Asia and it is east asian and not south asian.It is more likely to have more in common with SEA than SA.SAARC is a useless org and a waste of China's resources and assets.It should instead concentrate on plucking bhutan,south tibet out of Indian occupation and again a part of sinosphere.Let the SAsians fumble off,it is not of muh concern to China,except Pakistan which is a strategic ally of China and one of almost indispensable nature for future Chinese rise and keeping India in check