I think it's particularly egregious that they use such a lossy encoding. I can't read the hanzi, but at least "Hùn yuán" would have been more helpful, or even "Hu4n yua1n" would have enabled me to pronounce it or look it up without having the context to guess which characters it was representing.
Yes, this is very annoying, because how Pinyin works. There were a lot mistakes made when using Pinyin in English content. Pinyin suppose to break at character level, Pinyin = Pin Yin, you can easily write it as Pin-Yin, or Pin Yin, but Pinyin is just wrong.
Hun Yuan is a lot better. I agree, with unicode, we can easily incorporate the tone.