That's not a contradiction: that linked article says that India may have already overtaken China, this post's article says that the fertility rate in India has

That's not a contradiction: that linked article says that India may have already overtaken China, this post's article says that the fertility rate in India has dropped below replacement rate. The latter only signals the beginning of population decline; it hasn't actually started declining. China's population has been declining for a while because they have been below the replacement rate for a while.