Yes, that is correct behavior. We cannot expect natural language processing to detect language from just numbers. It has to be a semantic statement in a given language.
However, there is a workaround for your problem. In your case, Text analyzer fails to detect language. You can force Text Analyzer to fallback to a language if language is undetected. This setting is found on 'Advanced' tab on Text Analyzer - Enable fallback language if the language is undetected