So the German reader will read the English article (in English, not auto-translated), see the word billion, think “oh that looks familiar” and might assume it means the same as the German word Billion.

Machine translation makes quite a few mistakes, so I think if you have some decent knowledge of a language, you might be better off reading the original rather than a machine translation. At least my point of view from a couple of years ago. But it's also possible that machine translation has gotten WAY better in the last couple of years, I'm not sure.