This is actually a huge site that has well over 95% of the content in all languages already. There are only a small number of pages in each language that simply don't have corresponding pages in the other languages. There is a strong commitment and budget to translate all this content into the respective languages, but for various reasons certain pages and topics simply won't be translated. For example, there are some products that the company can only sell and market in Japan, so they feel there's no reason for them to put the content into English or Chinese. Occasionally there may be the odd press release that they only want in Japanese to comply with local regulations that wouldn't make sense in the other languages. Other than that most everything else has corresponding content.
It's a small percentage of pages where the 1-to-1 relationship breaks down for each language site. Also, for press releases and new content there's often a translation lag for the content among the languages. It could take up to a week to translate some content. In that time there would be nothing to link to.
Since the majority of the content is there in all languages the 1-to-1 links work most of the time. I have crushed all plans to try to switch the language based on IP or system language settings. These are manual links that are primarily for the users, although I'd hoped for some cross-pollination on the SEO front as well.
