When it becomes not true if you explicitly add the words that the speaker knows the listener inferred in the communication context. In your example, those impli

When it becomes not true if you explicitly add the words that the speaker knows the listener inferred in the communication context. In your example, those implied words are "The reason I was late is". The difficulty is in agreeing on or proving what those words were in that specific context, and whether the speaker knew it. It could instead of a case of mismatched assumptions based on different cultural backgrounds, which you see addressed in a lot of advice about working in other countries.